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Water-free transportation (WFT) causes shrimp (Penaeus vannamei) flesh quality deterioration. However, the roles of endogenous protease-induced protein hydrolysis have been neglected in the research. In the present study, calpain zymography, gelatinase zymography, the hematoxylin–eosin staining method, and other methods were applied to investigate the response of various endogenous proteases (cathepsin, calpain, and gelatinase), the myofibril fragmentation index (MFI), and the microscopic morphology of shrimp muscle during WFT in comparison with the shrimp under the conventional water transportation strategy (WT). The results showed that the total activity of proteases in shrimp muscle increased significantly (p ≤ 0.05) after simulated transportation. Cathepsins and gelatinases were activated during WFT. No significant (p > 0.05) changes of the activity of caspase-3 and the muscle cell apoptosis rate were detected in shrimp muscle cells after WFT. In addition, the MFI increased and the gap among muscle fiber bundles enlarged after WFT. Compared with WFT, no significant (p > 0.05) effect on the activities of calpain, gelatinase, and caspase-3 in the muscle of shrimp was found after WT, and only the activity of cathepsin L significantly increased (p ≤ 0.05). Based on the findings, we concluded that the activation of various endogenous proteases was induced during WFT. [ABSTRACT FROM AUTHOR]

NaCl is the main curing agent in dry-cured meat products, and a large amount of NaCl addition leads to high salt content of final products. Salt content and composition are important factors affecting the activity of endogenous proteases, which in turn could affect proteolysis as well as the quality of dry-cured meat products. With the increasing emphasis on the relationship between diet and health, reducing sodium content without sacrificing quality and safety of products is a great challenge for dry-cured meat industry. In this review, the change of endogenous proteases activity during processing, the potential relationship between sodium reduction strategy, endogenous proteases activity, and quality were summarized and discussed. The results showed that sodium replacement strategy and mediated-curing had a complementary advantage in influencing endogenous proteases activity. In addition, mediated-curing had the potential to salvage the negative effects of sodium substitution by affecting endogenous proteases. Based on the results, a sodium reduction strategy that sodium replacement in conjunction with mediated-curing based on endogenous proteases was proposed for the future perspective. [ABSTRACT FROM AUTHOR]

Dry-cured meat products are considerably popular around the world due to unique flavor. Proteolysis is one of the enzymatic reactions from which flavor substances are derived, which is affected by endogenous proteases. The purpose aimed to reveal the potential relationship between endogenous proteases and key flavor substances in dry-cured pork coppa in this paper. The dynamic changes of endogenous proteases activity, free amino acids, and volatiles during dry-cured pork coppa processing were characterized. The results showed that 5 kinds of free amino acids, Glu, Lys, Val, Ala, and Leu, were identified as significant contributors to taste. Meanwhile, key volatiles, such as hexanal, nonanal, octanal, benzaldehyde, 3-methyl butanoic acid, 2-methyl propanoic acid, and ethyl octanoate, greatly contributed to the flavor characteristics of dry-cured pork coppa. Further partial correlation analysis was performed to better elucidate the relationship among parameters. The results revealed that close relationship between endogenous proteases and key substances. RAP not only significantly affected the accumulation of key active-amino acids, but also affected the accumulation of ethyl octanoate, 2,3-pentanedione, and 2,3-octanedione by regulating the accumulation of octanoic acid and Leu. In addition, cathepsin B and D, DPP Ⅱ, DPP Ⅳ and RAP notably affected accumulation of hexanal.

Water-free transportation (WFT) causes shrimp (Penaeus vannamei) flesh quality deterioration. However, the roles of endogenous protease-induced protein hydrolysis have been neglected in the research. In the present study, calpain zymography, gelatinase zymography, the hematoxylin–eosin staining method, and other methods were applied to investigate the response of various endogenous proteases (cathepsin, calpain, and gelatinase), the myofibril fragmentation index (MFI), and the microscopic morphology of shrimp muscle during WFT in comparison with the shrimp under the conventional water transportation strategy (WT). The results showed that the total activity of proteases in shrimp muscle increased significantly (p ≤ 0.05) after simulated transportation. Cathepsins and gelatinases were activated during WFT. No significant (p > 0.05) changes of the activity of caspase-3 and the muscle cell apoptosis rate were detected in shrimp muscle cells after WFT. In addition, the MFI increased and the gap among muscle fiber bundles enlarged after WFT. Compared with WFT, no significant (p > 0.05) effect on the activities of calpain, gelatinase, and caspase-3 in the muscle of shrimp was found after WT, and only the activity of cathepsin L significantly increased (p ≤ 0.05). Based on the findings, we concluded that the activation of various endogenous proteases was induced during WFT.

Summary: Fish is susceptible to spoilage for enzymatic and microbial activities during storage, proteolysis of MPs by endogenous proteases played a crucial influence in the early postmortem decomposition of myosin. This study aimed to investigate the impact of stable chlorine dioxide (ClO2) combined with slightly acidic electrolyzed water (SAEW) on myofibrillar proteins (MPs) and endogenous proteases alterations in large yellow croaker (Pseudosciaena crocea) during cold storage. The results of Fourier‐transform infrared spectroscopy (FT‐IR) and intrinsic fluorescence intensity (IFI) showed that the ClO2 + SAEW treatment kept the structural stability of protein in fillets during cold storage. Moreover, ClO2 + SAEW treatment dramatically inhibited protein degradation and oxidation. The results of light microscopy further confirmed the results. Meanwhile, there was a tendency to first increase and then decrease on the activities of calpain and cathepsin B, L. According to the correlation analysis and principal component analysis, the activities of endogenous proteases (cathepsin B, D, L, and calpain) were significant (P < 0.01) positively correlated to myofibrillar fragmentation index and trichloroacetic acid‐soluble peptide, and were significant (P < 0.01) negative correlated with the contents of total sulfhydryl and Ca2+‐ATPase. The endogenous proteases activities and protein deterioration were strongly associated. Therefore, endogenous protease was affected by ClO2 and SAEW, which delayed protein degradation in large yellow croaker, especially ClO2 combined with SAEW treatment. [ABSTRACT FROM AUTHOR]

为了对薄壳山核桃仁中的主要蛋白质，特别是相对丰度较低的功能活性蛋白进行系统研究，以新鲜的薄壳山核桃仁为原料，利用电泳、液相串联质谱和氨基酸分析等方法，考察了薄壳山核桃仁的主要蛋白质和功能活性蛋白（抗氧化酶、内源性蛋白酶），并对内源性蛋白酶的最适pH和温度进行了研究。结果显示：薄壳山核桃仁的主要蛋白质包括11S球蛋白（58%）、7S球蛋白（17%）和9 kDa蛋白（15%），还含有0.239%超氧化物歧化酶、0.190%过氧化氢酶和0.282%内源性蛋白酶；只检测到1种蛋白酶抑制剂，并且其相对丰度极低；内源性蛋白酶在pH 3.5~5.5和40~60 ℃时可发挥水解活性，并在pH 4.5和50 ℃时活性最强；在氨基酸组成方面，薄壳山核桃仁蛋白的赖氨酸含量低（3.74%），但谷氨酸+谷氨酰胺含量（19.51%）和精氨酸含量（14.12%）高。说明国产薄壳山核桃适宜鲜食，对促进人体健康有益。 In order to systematically examine the major proteins in pecan kernels, especially the bioactive proteins with low relative abundance, the major proteins and bioactive proteins(antioxidant enzymes, endogenous proteases) in fresh pecan kernels were investigated by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis, liquid chromatography tandem mass spectrometry and amino acid analysis.The optimum pH and temperature of the endogenous proteases were also studied. The results showed that the major proteins in pecan kernels included 11S globulins (58%), 7S globulins (17%) and 9 kDa proteins (15%), as well as 0.239% superoxide dismutases, 0.190% catalases and 0.282% endogenous proteases. Only one protease inhibitor was detected, and its relative abundance was extremely low. These endogenous proteases showed hydrolytic activity at pH 3.5-5.5 and 40-60 ℃, and optimal at pH 4.5 and 50 ℃. As for the amino acid composition, the proteins in pecan kernels contained a low content of lysine (3.74%), but a high content of glutamic acid + glutamine (19.51%) and arginine (14.12%). It is suggested that domestic pecans are suitable for fresh consumption, which is benifical for promoting human health.

Endogenous proteases are significant for Jinhua ham quality. Protein degradation affects the chemical traits, texture and the formation of flavor substances. Protease activities are affected by different process parameters, such as processing temperature, maturation time, salt content and the drying rate. They affect ham quality, which can be controlled by process parameters. The influences of key factors on Jinhua ham quality are briefly summarized, which can provide a theoretical basis for the selection of specific parameters in dry-cured ham processing. Furthermore, some suggestions are proposed for correcting and improving the flavor and textural defects of ham, yet the effectiveness depends on the operating conditions. The determination of enzyme activity is not real-time and unsupervised at the moment. Future research will focus on the determination of the actual endogenous protease activity and the quantitative relationship between the enzyme activity and main processing parameters. [ABSTRACT FROM AUTHOR]

Autolysis technology has shown potential for protein hydrolysates production from marine and aquaculture byproducts. Viscera are a source of cheap proteolytic enzymes for producing protein hydrolysates from the whole fish or processing byproducts of the most valuable commercial species by applying autolysis technology. The use of autolysis allows economical production of protein hydrolysate and provides an opportunity to valorize downstream fish and shellfish processing byproducts at a lower cost. As a result, production and application of marine byproduct autolysates is increasing in the global protein hydrolysates market. Nevertheless, several restrictions occur with autolysis, including lipid and protein oxidation mediated by the heterogeneous composition of byproducts. The generally poor storage and handling of byproducts may increase the formation of undesirable metabolites during autolysis, which can be harmful. The formation of nitrogenous compounds (i.e., biogenic amines), loss of freshness, and process of autolysis in the byproducts could increase the rate of quality and safety loss and lead to more significant concern about the use of autolysates for human food applications. The current review focuses on the autolysis process, which is applied for the hydrolysis of aquaculture and marine discards to obtain peptides as functional or nutritive ingredients. It further addresses the latest findings on the mechanisms and factors contributing the deterioration of byproducts and possible ways to control oxidation and other food quality and safety issues in raw materials and protein hydrolysates. [ABSTRACT FROM AUTHOR]

为筛选适合水媒法加工的花生品种，降低花生蛋白的致敏性，收集了5个花生品种，首先比较了其脂质和蛋白质含量，然后采用水媒法提取分离蛋白质与脂质，考察了花生品种对脂质和蛋白质的提取率及脂质和蛋白质的分离效果的影响，最后比较了不同品种花生的内源性蛋白酶（内肽酶和外肽酶）活性。结果表明：脂质（46.95%～51.35%）和蛋白质（24.66%～29.68%）含量在花生品种间存在差异；花生品种对于蛋白质提取率（91.86%～97.77%）的影响显著，而对于脂质提取率（98%左右）的影响不大；不同品种花生浆中蛋白质和脂质的离心分离效果不同，蛋白质在蛋白液中的分布比例为85.32%～97.34%，脂质在乳状液中的分布比例为68.75%～81.24%，白沙308的分离效果最好；内源性蛋白酶活性（pH 3～5）在花生品种间存在差异，但是各品种的内肽酶均在pH 3时表现出最强活性，可有效水解花生致敏蛋白Ara h 1；各品种花生的外肽酶活性均随pH的增加而增加，在pH 5时，四粒红最高；对于内肽酶和外肽酶的协同活性，花育在pH 3时最强，而其他4个品种在pH 5时最强。综上，白沙308可作为花生水媒法加工的参考品种，而四粒红的内源性蛋白酶活性最强。 In order to screen peanut varieties suitable for aqueous extraction processing and reduce the allergenicity of peanut protein, five peanut varieties were collected for study. Firstly, their lipid and protein contents were compared, and the protein and lipid was extracted and separated by aqueous extraction processing. Then, the effects of peanut variety on extraction rates of lipid and protein, and separation efficiency of lipid and protein were investigated. Finally, the activities of endogenous proteases (endopeptidases and exopeptidases) of different peanut varieties were compared. The results showed that the lipid (46.95%-51.35%) and protein (24.66%-29.68%) contents were different among peanut varieties. The protein extraction rate (91.86%-97.77%) was obviously affected by varieties, while the lipid extraction rate (about 98%) was not. The effects of centrifugal separation of protein and lipid in different varieties of peanut milk were different. The distribution proportion of protein in protein liquid was 85.32%-97.34%, whereas the distribution proportion of lipid in emulsion was 68.75%-81.24%. Baisha 308 was the best for the centrifugal separation of lipid and proteins. Endogenous protease activity in the range of pH 3-5 was different among peanut varieties, but the endopeptidases in all varieties showed the highest activity at pH 3, which could effectively hydrolyze the allergen protein Ara h 1. The activity of exopeptidases in all varieties enhanced with the increase of pH. At pH 5, Silihong exerted the highest exopeptidase activity. Huayu showed the highest synergistic activity of endopeptidases and exopeptidases at pH 3, while the other four varieties were the highest at pH 5. In conclusion, Baisha 308 can be used as a reference variety for peanut aqueous extraction processing, and the endogenous protease activity of Silihong is the strongest.

This study aimed to explore the effect of ultra-high pressure (UHP) treatment (100–500 MPa, 5 min, 15 ± 1 ℃) on the relationship between endogenous proteases and protein degradation of Yesso scallop (Mizuhopecten yessoensis) adductor muscle during iced storage for 28 days. Our findings showed that the UHP treatment kept the water holding capacity stable, increased the hardness and decreased the springiness of scallop adductor muscle during iced storage. 400 and 500 MPa UHP treatments caused protein denaturation and oxidation significantly, decreased protein degradation rate and inhibited the activities of endogenous proteases. According to the correlation analysis, the activities of cathepsin B, D, H, L, calpain and serine protease were positively correlated with TCA-soluble peptides. The activities of endogenous proteases were significantly correlated with protein degradation. Therefore, the effect of UHP on endogenous protease caused the protein degradation rate to slow down and prevented the texture deterioration in scallops.

Sesame seeds is recognized as a good source of lipids and proteins, and its processing is mainly focused on oil production. Sesame is rich in a variety of essential amino acids for human body, which has great development and utilization value. However, the processing of sesame proteins is limited by its poor solubility. Due to the sustainability, economical costs and health benefits of plant proteins, researchers have greatly increased their interest in them. At present, aqueous extraction processing has the capability to realize the comprehensive utilizations of lipids and proteins in sesame. However, the cost of commercial proteases is considerable for large scale applications. Previous studies in our laboratory have confirmed that endogenous proteases in sesame seeds have high activity, and it has great potential for aqueous extraction processing of sesame. While preparing lipid products, endogenous proteases could be used to biologically convert sesame proteins into hydrolysate with high solubility and nutritional function. In addition, in the previous study, the effects of pH value, temperature, and time on proteolytic activity of endogenous proteases in sesame milk were studied, and the proteins were optimally hydrolyzed at pH 4.5 value and 50 ℃ for 6 h catalyzed by the endogenous proteases. In this paper, wet-peeled sesame was dried and pressed in order to obtain the sesame oil and pressed meal. Then, the pressed meal was then hydrolyzed into hydrolysate by endogenous proteases. And the effects of drying temperature on pressed oil yield and proteolytic activity of endogenous proteases in wet-peeled sesame were investigated, which provides reference for the practical applications of endogenous proteases. The results showed that under hydraulic pressing (80 MPa, 1 h), the oil yield of sesame and peeled sesame (50 ℃, 4 h) (the total lipids in sesame as 100%) were 81.76% and 83.57% respectively, indicating that peeling is conducive to the improvement of oil yield. The oil yield of wet-peeled sesame increased to 88.55%-90.98% after drying at 80-180 ℃ for 1 h. For the endogenous proteases, its activity decreased slowly at 80-130 ℃ and remained about 57% at 130 ℃, indicating that endogenous proteases had good thermal stability, then the activity decreased rapidly after 130 ℃ and inactivated at 180 ℃. In order to modify proteins in the pressed meal with endogenous proteases, sesame seeds were dried at 50 ℃ for 4 h to obtain sesame oil and low-denatured pressed meal. After grinding, the sesame milk prepared from pressed meal was incubated at pH 4.5 value and 50 ℃ for 6 h. And hydrolyzed sesame milk was separated into two fractions (skim and precipitation) by centrifugation (3 000 g, 5 min). The results showed that the proteins in the skim still accounted for 66% of total proteins in sesame milk after centrifugation, and the proteins in skim were composed of 38% small peptides (< 1 500 Da) and 37% free amino acids. In addition, there are many bioactive substances in the skim, such as ornithine, serotonin, DL-dopa and so on. The purposes of this study were to evaluate the thermal stability of endogenous proteases in sesame seeds and to develop a new method for production of sesame protein hydrolysate, which enhanced the solubility and bioactive properties of sesame proteins. [ABSTRACT FROM AUTHOR]

Endogenous proteases are significant for Jinhua ham quality. Protein degradation affects the chemical traits, texture and the formation of flavor substances. Protease activities are affected by different process parameters, such as processing temperature, maturation time, salt content and the drying rate. They affect ham quality, which can be controlled by process parameters. The influences of key factors on Jinhua ham quality are briefly summarized, which can provide a theoretical basis for the selection of specific parameters in dry-cured ham processing. Furthermore, some suggestions are proposed for correcting and improving the flavor and textural defects of ham, yet the effectiveness depends on the operating conditions. The determination of enzyme activity is not real-time and unsupervised at the moment. Future research will focus on the determination of the actual endogenous protease activity and the quantitative relationship between the enzyme activity and main processing parameters.

Summary: Effects of endogenous enzymes on texture deterioration of Macrobrachium rosenbergii during frozen storage (−18 °C) were investigated. The prawn was pretreated with iodoacetic acid (IAA) solution to inhibit cysteine proteases and/or phenylmethylsulfonyl fluoride (PMSF) solution to inhibit trypsin before frozen storage, and sterile distilled water was used as the control. After 16 weeks of cryopreservation, the shear force of the groups treated with enzyme inhibitors was significantly higher than that of sterile distilled water‐treated group (control; P < 0.05), while significantly fewer TCA‐dissolved peptides, α‐amino nitrogen and Myofibril fragmentation index (MFI) value were observed in all inhibitor‐treated groups (P < 0.05). Compared with PMSF treatment, IAA or IAA + PMSF treatment effectively alleviated softening and remarkably reduced the accumulation of TCA‐soluble peptides and AAN (α‐amino nitrogen) during frozen storage, with a lower MFI value and a higher sodium dodecyl sulphate‐polyacrylamide gel electrophoresis band intensity. Therefore, endogenous cysteine proteases in muscle play a crucial part in texture deterioration of giant freshwater prawn during cryopreservation. [ABSTRACT FROM AUTHOR]

• Endopeptidases and exopeptidases were examined in mung bean protein extract. • 8S and 11S globulins on SDS–PAGE gel were confirmed in our experimental conditions. • 11S (except at pH 3–3.5) and 8S globulins showed strong resistance to the endopeptidases. • Exopeptidases preferred to liberate methionine and tryptophan. • Endopeptidases and exopeptidases negatively affected the yield of mung bean protein. Mung bean protein possesses several health benefits, and aqueous processing methods are used for its production. However, mung bean protein yields are different with different methods, which are actually different in conditions (e.g., pH, temperature, and time). Herein, liquid chromatography tandem mass spectrometry identified 28 endopeptidases and exopeptidases in mung bean protein extract, and the positions of 8S and 11S globulins on sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) gel were confirmed in our experimental conditions. The SDS–PAGE, trichloroacetic acid–nitrogen solubility index, and free amino acid analysis revealed that (1) 8S globulins showed strong resistance to the endopeptidases (optimal at pH 5 and 50 °C) at pH 3–9, and 11S globulin exhibit strong resistance expect at pH 3–3.5; (2) the exopeptidases (optimal at pH 6 and 50 °C) preferred to liberate methionine and tryptophan. These proteases negatively affected protein yield, and short production time and low temperature were recommended. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the influence of rice wine (Jinbiao, Yinbiao, Wunianchen, Nv'erhong) on the endogenous protease activity, myofibrillar degradation, and quality characteristics of topmouth culter (Culter alburnus). Rice wine had a pH of 4.3 and calcium ions ranging from 89.30 to 123.70 μg/mL. Nv'erhong rice wine had the highest total phenolic content of 583.38 μg gallic acid equivalent (GAE)/mL, while Wunianchen rice wine (WNC) showed the strongest total antioxidant capacity of 87.29 U/mL. WNC presented the optimum inhibitory effect on endogenous proteases of calpain and cathepsin B, D, and L, delaying the degradation of myosin heavy chain and α-actinin, which are important to muscle softening. The quality characteristic evaluation indicated that the addition of rice wine could maintain the hardness and chewiness, increase the springiness of the fish fillet, as well as inhibit the total volatile basic nitrogen production. These results suggest that rice wine had effects of inhibiting endogenous proteases, delaying myofibrillar degradation, and maintaining the sensory quality of topmouth culter. [ABSTRACT FROM AUTHOR]

Extensive proteolysis and formation of flavor substances occur during the processing of dry-salted fish due to the action of endogenous proteases. This study analyzed the evolution of the endogenous proteases and the relationship between endogenous protease levels and protein degradation during processing. Cathepsin B and L activity increased significantly during the last two stages, while cathepsin H activity decreased non-significantly (residual activity was 92.27%) compared to initial activity levels in fresh fish. Dipeptidyl peptidase (DPP I, IV) activity decreased overall. The activity of three aminopeptidases (arginine aminopeptidase; alanyl aminopeptidase; leucyl aminopeptidase) initially decreased (P

This study evaluated the food safety and proximate composition of shrimp head (SH). Potentially toxic elements in SH were below European Union legislation limits. SH had a high content of tasting amino acids (sweet and umami amino acids was 57%) and a high content of functional amino acids (essential amino acids was 37%). Moreover, the changes of flavor and key umami molecules in SH were studied by sensory evaluation, electronic tongue, electronic nose, automated amino acid analyzer, and high performance liquid chromatography (HPLC). The results showed that the significant difference of flavor in SH happened during autolysis. SH with autolysis had the best umami taste at 6 h, which may result from the synergistic work of free amino acids and nucleotide related compounds. Additionally, the performance of endogenous proteases in SH was investigated to efficiently analyze autolysis. The optimum pH and temperature of endogenous proteases in SH were 7.5 and 50 °C, respectively. The autolysis of SH depends on two endogenous proteases (~50 kDa and ~75 kDa). These results suggest that the formation of flavor in SH during autolysis can be controlled, which could provide guidance for SH recycle. SH could consider as one of the food materials for producing condiments.

Inhibitors that control muscle softening are important for regulating the activities of specific proteinases in meat. Proteolytic activity of endogenous proteinases in postmortem fish leads to the deterioration of myofibres. Calpain proteolytic enzyme system in skeletal muscles is mainly responsible for the post-mortem proteolysis. Soluble sarcoplasmic serine proteinase and the insoluble myofibrillar serine proteinase fractions contribute to the modori effects in surimi gels while myosin heavy chains contribute to gel strength. Proteolytic degenerative processes negatively affect the entire quality spectrum of the fish as food. Legume seeds are a good source of proteinase inhibitors with the potential to emerge as a promising tool in fish meat quality management. Many workers have studied the potent inhibitory effect of the seed flour from various legume crops on the flesh, surimi gels and visceral proteinases of fishes. The present review provides collective information about proteolysis in fish and its control by using legume seed flour as a natural source of proteinase inhibitors. Use of legume seed flour can reduce the dependence of the meat processing industry on the non-renewable synthetic chemical agents. Moreover, the use of natural products from sustainable resources also leads to the improved economics of meat production. [ABSTRACT FROM AUTHOR]

Extensive proteolysis and formation of flavor substances occur during the processing of dry-salted fish due to the action of endogenous proteases. This study analyzed the evolution of the endogenous proteases and the relationship between endogenous protease levels and protein degradation during processing. Cathepsin B and L activity increased significantly during the last two stages, while cathepsin H activity decreased non-significantly (residual activity was 92.27%) compared to initial activity levels in fresh fish. Dipeptidyl peptidase (DPP I, IV) activity decreased overall. The activity of three aminopeptidases (arginine aminopeptidase; alanyl aminopeptidase; leucyl aminopeptidase) initially decreased (P < 0.05) then significantly increased (P < 0.05) during the final stage. Principal component analysis indicated that cathepsins B and L had larger influences than cathepsin H on protein degradation and flavor substance formation in dry-salted fish, but the influence of dipeptidyl peptidases and aminopeptidases on protein degradation and flavor substance formation was limited. [ABSTRACT FROM AUTHOR]

The autolysis of pretreated bovine skin (PBS) (treated with 0.1 M NaOH and 1% HCl), its endogenous proteases, inhibitors and their effects on quality attributes of gelatin were examined. PBS was subjected to different temperatures (20–90 °C) and pH (2–9) and treated with different protease inhibitors. Maximum autolytic activity of PBS was observed at 40 °C and pH 5. Ethylene-bis (oxyethylenenitrilo) tetraacetic acid (EGTA) was the most effective in impeding the degradation of γ-, β- and α- chains of PBS protein indicating that metallocollagenases were the predominant endogenous proteases in bovine skin. Gelatin was extracted in the absence (GAE) and presence (GPE) of EGTA, and EGTA with papain enzyme (GPEP). GPEP had a higher yield and lower gel strength than GEA and GPE. Metallocollagenases partook in the degradation of gelatin thereby affecting its functional properties. Pretreating PBS with or without EGTA, and papain influenced the quality attributes of gelatin. [ABSTRACT FROM AUTHOR]

Studies have demonstrated that protease-activated receptors (PARs) with four subtypes (PAR1-4) are mainly expressed in the renal epithelial, endothelial, and podocyte cells. Some endogenous and urinary proteases, namely thrombin, trypsin, urokinase, and kallikrein released during diseased conditions, are responsible for activating different subtypes of PARs. Each PAR receptor subtype is involved in kidney disease of distinct aetiology. PAR1 and PAR2 have shown differential therapeutic outcomes in rodent models of type-1 and type-2 diabetic kidney diseases due to the distinct etiological basis of each disease type, however such findings need to be confirmed in other diabetic renal injury models. PAR1 and PAR2 blockers have been observed to abolish drug-induced nephrotoxicity in rodents by suppressing tubular inflammation and fibrosis and preventing mitochondrial dysfunction. Notably, PAR2 inhibition improved autophagy and prevented fibrosis, inflammation, and remodeling in the urethral obstruction model. Only the PAR1/4 subtypes have emerged as a therapeutic target for treating experimentally induced nephrotic syndrome, where their respective antibodies attenuated the podocyte apoptosis induced upon thrombin activation. Strikingly PAR2 and PAR4 subtypes involvement has been tested in sepsis-induced acute kidney injury (AKI) and renal ischemia-reperfusion injury models. Thus, more studies are required to delineate the role of other subtypes in the sepsis-AKI model. Evidence suggests that PARs regulate oxidative, inflammatory stress, immune cell activation, fibrosis, autophagic flux, and apoptosis during kidney diseases. • Inhibition of PAR1 attenuates kidney disease in type-1 diabetic mice. • Compensatory increase of renal PAR1 expression in PAR2−/− mice. • Dual PAR1 and PAR2 blockade a promising therapy for diabetic kidney disease. • Up-regulation of PAR4 worsens renal ischemia-reperfusion injury. • Blockade of PAR2 reduces renal inflammation in sepsis. [ABSTRACT FROM AUTHOR]

Lizardfish is a major ingredient for the manufacture of surimi in Japan, and its viscera are considered a novel source of protease to enhance protein autolysis. We investigated the non-volatile taste components of fish sauce produced from the lizardfish Saurida wanieso viscera in order to clarify the effects of fermentation conditions on the quality of fish sauce. Samples were fermented for 40 days under three sets of conditions: group 1, pH 7.0 and 60 °C; group 2, pH 11.0 and 40 °C; and group 3, uncontrolled pH and ambient temperature. Group 2 showed the highest concentration of umami amino acids (1,195.29 mg/100 ml) and sweet amino acids (2,033.60 mg/100 ml). High levels of lactic acid (1,219.65 mg/100 ml), acetic acid (367.08 mg/100 ml), and pyroglutamic acid (261.66 mg/100 ml) were also found in group 2. In addition, investigation of nucleic acid-related compounds revealed differences in the degree of nucleotide hydrolysis among the three groups during fermentation. Sensory evaluation showed that group 2 had the highest umami and the lowest bitterness, indicating that this group had the most preferable taste. These results reveal that fermentation under conditions optimal for endogenous proteases is beneficial for producing a product with optimal taste qualities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gel deterioration was attributed to endogenous proteases in shrimp head and meat. • Shrimp head endogenous protease degraded the myosin heavy chains. • Rinsing removed endogenous proteases and concentrated salt-soluble proteins. • Deheading and rinsing (1–2 times) pretreatment could improve the gel of the shrimp surimi. In this study, the effects of different pretreatments on the quality of white leg shrimp surimi were investigated based on shrimp endogenous proteases. The results showed that removing the head and rinsing significantly (P < 0.05) improved the gel strength, texture, whiteness, water distribution, and microstructure of the shrimp surimi gels. Headless shrimp surimi (HSS) had higher salt-soluble protein and lower water-soluble protein than whole shrimp surimi (WSS). The shrimp heads had high cathepsin B, L, D, and serine protease activities. Electrophoretic analysis revealed significant degradation of the myofibrillar proteins in the WSS during cold storage and thermal gelation. Moreover, the myosin heavy chains almost disappeared after thermal gelation, and new bands appeared at about 270 kDa and 100 kDa. However, rinsing reduced the endogenous proteases, water-soluble proteins, and concentrated salt-soluble proteins in the shrimp surimi; thus, the quality of the shrimp surimi gel improved after rinsing. These results suggest that the quality of the surimi gel was damaged by the endogenous proteases, and that removal of the shrimp heads and rinsing significantly (P < 0.05) improved the quality of the shrimp surimi gel. The gel properties of WSS were similar after the second rinse to those of unrinsed HSS. The choice of headless shrimp or whole shrimp as the raw material for production needs to be comprehensively considered according to the planned cost and the quality required for the shrimp surimi product. The recommended number of rinses is 1–2. [ABSTRACT FROM AUTHOR]

• Hydrolysis behaviors of endogenous proteases on sesame milk proteins were examined. • Endogenous proteases randomly cleaved the cleavable peptide bonds on 11S globulins. • Cleavage specificity of serine carboxypeptidases on sesame proteins was clarified. • Lipids and proteins in hydrolyzed sesame milk were easily separated by centrifugation. • Low-phytate sesame protein hydrolysate with good solubility was obtained. Endogenous proteases with high activity have been identified in sesame seeds. However, the hydrolyzing behaviors of endogenous proteases on proteins in sesame milk are not well understood. In this study, the endogenous proteases optimally hydrolyzed proteins at pH 4.5 and 50 °C for 6 h. Tricine–sodium dodecyl sulphate–polyacrylamide gel electrophoresis and liquid chromatography tandem mass spectrometry analyses revealed that endogenous proteases randomly cleaved the cleavable peptide bonds on 11S globulins, and amino acid analysis indicated that serine carboxypeptidases preferentially cleaved tryptophan, phenylalanine, methionine, tyrosine, and leucine. The hydrolyzed sesame milk was separated into cream, transparent skim, and precipitate fractions by centrifugation (3000 g , 5 min). The major protein components in skim were 42% peptides (<1500 Da) and 35% free amino acids. The phytate in skim was greatly reduced by adjusting to neutral and alkaline pH. This study is meaningful at supplying a strategy for producing low-phyate sesame protein hydrolysate. [ABSTRACT FROM AUTHOR]

To elucidate the role of microbes and endogenous proteases in the formation of the taste-active components during processing of heshiko, a Japanese traditional seafood produced by aging salted mackerel with rice bran, the production of lactic acid, free amino acids, and acid-soluble peptides throughout the aging process was compared in the absence and presence of antibiotics including chloramphenicol, penicillin, and cycloheximide. Although viable counts on fish flesh on a 2.5% NaCl-GYP agar plate increased to 10 cfu/g with the aging process of heshiko in the absence of the antibiotics, adding the antibiotics suppressed the increase in viable counts to less than 10 cfu/g throughout the aging process. Lactic acid barely increased due to the suppression of microbial growth by the antibiotics. In spite of the inhibition of bacterial growth throughout the processing of heshiko upon the addition of the antibiotics, little difference was observed in the production of free amino acids and acid-soluble peptides. These results suggest that, unlike lactic acid (which is a fermentation product of lactic acid bacteria), free amino acids and acid-soluble peptides are mainly produced through protein hydrolysis by endogenous proteases in mackerel meats during the aging process of heshiko. [ABSTRACT FROM AUTHOR]

Human brain glutamate decarboxylase 65 (hGAD65) was found to exist as full-length and truncated forms when the glutathione S-transferase-tagged hGAD65 fusion protein was subjected to factor Xa cleavage. The truncated form is produced by cleavage at arginine 69 based on N-terminal amino acid sequence analysis, and has a molecular weight of 58 kD. It is resistant to further factor Xa cleavage or mild trypsin treatment and is more active and more stable than the full-length form. Both the full-length and truncated forms of GAD are also observed in brain preparations in the presence of protease inhibitors. Furthermore, full-length GAD could be converted to the truncated form by endogenous proteases, suggesting that the conversion of full-length to truncated GAD mediated by endogenous protease may represent an important mechanism in the regulation of GABA biosynthesis in the brain.Copyright © 2003 National Science Council, ROC and S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Ultrastructural changes and glutathione level were investigated in the pectoralis muscle of rats fed a low-protein diet. Electron microscopy demonstrated the ultrastructural changes of occasional myofibrils affected with protein deficiency that were characterized with the streaming and/ or disruption of the Z-line and disintegration of sarcomeric striation. In the affected sarcomeres, sarcomere length was often elongated and fragmented thick filaments were present together with dense amorphous materials flowing from the damaged Z-line. Glutathione level of muscle in the low-protein diet group (5%casein) was reduced to about one-third of that in the control diet group (20% casein). The study suggests that depletion of glutathione by protein malnutrition is responsible for inducing myofibrillar damage through the excess leaking of Ca[sup 2+] into the cytosol. [ABSTRACT FROM AUTHOR]

• Endopeptidases and exopeptidases were characterized in peanut seeds. • Aspartic endopeptidases and legumain exerted in vitro activity at pH 2–5. • Exopeptidases had low in vitro proteolytic activity at pH 2–5. • Endopeptidases induced the limited hydrolysis of Ara h 1 and arachin. • Endopeptidases degraded the IgE-binding epitopes of Ara h 1 to some extent. Research concerning the utilization of oilseed endogenous proteases is scarce. Herein, we investigated the peanut proteases and their effects on peanut proteins. Liquid chromatography tandem mass spectrometry analysis showed that peanut contained several endopeptidases and exopeptidases. Protease inhibitor assay and analysis of cleavage sites showed that the obvious proteolytic activity at pH 2–5 and 20–60 °C was from aspartic endopeptidases (optimal at pH 3) and one legumain (pH 4). The above endopeptidases destroyed five and six IgE-binding epitopes of Ara h 1 at pH 3 and 4, respectively. Ara h 1 (>95%) and arachin (50–60%) could be hydrolyzed to generate 10–20 kDa and <4 kDa peptides at pH 3, which was enhanced by the pH 3 → 4 incubation. Further, the limited hydrolysis improved the gel-forming ability and in vitro digestibility (approximately 15%) of peanut proteins. Free amino acid analysis showed that the activity of exopeptidases was low at pH 2–5. [ABSTRACT FROM AUTHOR]

This study evaluated the food safety and proximate composition of shrimp head (SH). Potentially toxic elements in SH were below European Union legislation limits. SH had a high content of tasting amino acids (sweet and umami amino acids was 57%) and a high content of functional amino acids (essential amino acids was 37%). Moreover, the changes of flavor and key umami molecules in SH were studied by sensory evaluation, electronic tongue, electronic nose, automated amino acid analyzer, and high performance liquid chromatography (HPLC). The results showed that the significant difference of flavor in SH happened during autolysis. SH with autolysis had the best umami taste at 6 h, which may result from the synergistic work of free amino acids and nucleotide related compounds. Additionally, the performance of endogenous proteases in SH was investigated to efficiently analyze autolysis. The optimum pH and temperature of endogenous proteases in SH were 7.5 and 50 °C, respectively. The autolysis of SH depends on two endogenous proteases (~50 kDa and ~75 kDa). These results suggest that the formation of flavor in SH during autolysis can be controlled, which could provide guidance for SH recycle. SH could consider as one of the food materials for producing condiments. [ABSTRACT FROM AUTHOR]

• Endogenous proteases cause texture deterioration of scallop during cold storage. • Endogenous cysteine proteases mainly degrade myofibrillar proteins. • Endogenous serine proteases degrade myofibrillar and connective tissue proteins. • Endogenous proteases cause the changes of microstructure and the reduction of WHC. • Serine- and cysteine-protease inhibitors prevent the texture deterioration. Texture deterioration occurs in adductor muscle of scallop (Argopecten irradians) (AMS) after 5 d of cold storage. Principal component analysis indicated the texture deterioration resulted in significant decrease of hardness, springiness, adhesiveness and chewiness, but significantly increased cohesiveness. Endogenous proteases degraded structural proteins, among which cysteine proteases were mainly responsible for myofibrillar proteins (MPs) degradation, while serine proteases degraded both MPs and connective tissue proteins. Pearson coefficient analysis showed that texture indicators significantly correlated with structural protein indicators in AMS. To be more specific, the hardness, springiness, adhesiveness and chewiness negatively correlated with myofibrillar fragmentation index, soluble hydroxyproline (Hyp) and soluble glycosaminoglycans, but positively correlated with solubility of MPs and water holding capacity. Meanwhile, the cohesiveness positively correlated with soluble Hyp. The Taylor diagram and Hierarchical cluster analysis confirmed that the inhibitors of cysteine and serine proteases could effectively retard textural deterioration of AMS during 5 d of cold storage. [ABSTRACT FROM AUTHOR]