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Background Designer lipid is a novel, health-friendly lipid with potential application in food, nutraceutical and pharmaceutical industries, including obesity, cancer, heart disease, inflammation. These advantages arise due to modification of fat/oil by the chemical or enzymatic process to form designer lipid. The transformation of lipid results in the rearrangement of fatty acid within a triglyceride molecule or between two different triglycerides. Thus, the resulting designer lipid has superior and unique physicochemical properties than the naturally occurring triglycerides. Due to these excellent physicochemical properties, they are in great demand in the market. Scope and approach The primary aim of this review is to describe component fatty acids used for the synthesis of designer lipids, the process used in designing designer lipids, and reactors used to intensify the yield of designer lipids, application of designer lipid in the food and nutraceutical sector. Key findings and conclusions Designer lipid is a chemically/enzymatically modified form of lipid to improve physicochemical and nutritional properties of traditional lipids coming from plant and animal source. Such fabricated lipids have attracted consumers' attention because of their unique properties and capability to manage various syndromes. Their demand by the consumer increased over the recent past. To fulfil the increase in demand, the intensified synthesis of these designer lipids is carried out using packed bed reactors, ultrasonic reactors, high-pressure reactors. With their claimed health benefits, designer lipids are widely used as a functional ingredient in the food and pharmaceutical industries. Currently, designer lipids are used as a plastic fat, human milk substitute, cocoa butter, used in infant formulation, low-calorie lipids, an anti-cancer, reduced cardiovascular risk etc. The application of designer lipid is governed by the positional distribution and type of fatty acid esterified on the glycerol backbone.

DNA double-strand break (DSB) resection, once thought to be a simple enzymatic process, is emerging as a highly complex series of coordinated activities required to maintain genome integrity. Progress in cell biology, biochemistry, and genetics has deciphered the precise resecting activities, the regulatory components, and their ability to properly channel the resected DNA to the appropriate DNA repair pathway. Herein, we review the mechanisms of regulation of DNA resection, with an emphasis on negative regulators that prevent single-strand (ss)DNA accumulation to maintain genome stability. Interest in targeting DNA resection inhibitors is emerging because their inactivation leads to poly(ADP-ribose) polymerase inhibitor (PARPi) resistance. We also present detailed regulation of DNA resection machineries, their analysis by functional assays, and their impact on disease and PARPi resistance.

The enzymatic carbon fixation is a promising approach to deal with greenhouse gas emission and is usually accompanied with energy consumption during the reduction of CO2. As a very important route, the carboxylation can convert CO2 to organic carbon without extra requirement of reduction power and is hoped as a greener solution, especially for some non-bulk chemicals, such as medical intermediates. Here, a concept-proof trail of green enzymatic process of conversing both of CO2 and benzene to produce 2,3-dihydroxybenzoic acid (2,3-DHBA), which is the intermediate for fine chemicals, is introduced with O2 from air and glucose. The results showed that the conversion catechol by 2, 3-dihydroxybenzoic acid decarboxylase (2,3-DHBD) alone was around 30 %, with an overall conversion from phenol of 2.4 %, which was limited by the in-situ production of catechol. This trail contributed a green enzymatic route for the production of 2,3-DHBA.

The aim of this study was to analyze the effects of a rotating magnetic field (RMF) on the activity and stability of horseradish peroxidase (HRP) and the catalyzed enzymatic process. It was found that 8 h of exposure to RMF does not influence the operational stability of HRP. At the same time, it was observed that the RMF improved HRP activity in a wider range of pH: 49% and 68% at pH 6.5 and pH 7.0, respectively. The efficiency of the catalyzed enzymatic process under exposure to RMF was analyzed by two-dimensional correlation analysis (2DCorr) on the example of the Remazol Brilliant Blue R (RBBR) decolorization process. The obtained results indicated the influence of RMF on the intensification of this process. Our studies showed an alternative method of enzymatic process intensification, which is significant in science and has practical value for applications.

Background: Mathematical modeling is useful in the analysis, prediction, and optimization of an enzymatic process. Unlike the conventional modeling methods, Monte Carlo method has special advantages in providing representations of the molecule’s spatial distribution. However, thus far, Monte Carlo modeling of enzymatic system is namely based on unimolecular basis, not suitable for practical applications. In this research, Monte Carlo modeling is performed for enzymatic hydrolysis of lactose for the purpose of real-time applications. Results: The enzyme hydrolysis of lactose, which is conformed to Michaelis–Menten kinetics, is modeled using the Monte Carlo modeling method, and the simulation results prove that the model predicts the reaction kinetics very well. Conclusions: Monte Carlo modeling method can be used to model enzymatic reactions in a simple way for real-time applications.How to cite: Gao L, Guo Q, Lin H, et al. Modeling of lactose enzymatic hydrolysis using Monte Carlo method. Electron J Biotechnol 2019;41.https://doi.org/10.1016/j.ejbt.2019.04.010 Keywords: β-Galactosidase, Enzymatic hydrolysis, Enzymes, Galactose, Hydrolysis, Immobilized, Lactose, Modeling, Monte Carlo, Silica gel, Stochastic, Tagatose

Celiac disease and non-celiac gluten sensitivity are both related to gluten consumption. In sensitive subjects, gluten triggers an immune-mediated enteropathy for which no therapy is yet available. Beer must be avoided by gluten sensitive subjects, since it is generally made from gluten containing grains such as barley and wheat. In this study we compared two different deglutinization treatments on an American India Pale Ale, brewed on a craft beer pilot plant: an enzymatic process based on Aspergillus niger prolyl endopeptidase and a precipitation process by silica gel. The gluten amount in all stages of brewing, and the effects of treatments on standard quality attributes, chemical composition and sensory profile were evaluated. Both treatments were able to reduce gluten level below 20 ppm, showing a different behavior. Only slight differences were observed in the chemico-physical characteristics of treated and untreated beers, whereas sensory analysis did not highlight any change. Industrial relevance Considering the massive increase of microbreweries and the grown of gluten-free products market, two different deglutinization treatment were compared in pilot plant production of craft beer. Results show how it is possible to produce a gluten-free beer from traditional ingredients. The slight differences observed between treatments had no impact on the sensory profile, allowing to brew high quality gluten-free beers.

The fate of estrogens in surface water is mainly dependent on two processes, i.e. photodegradation and biotransformation. Each of the separate process is invariably of interest, but research on the combination of the two processes has rarely been explored. In the present work, the transformation of 17α-ethinylestradiol (EE2) by simultaneous photochemical and enzymatic process in water was systematically investigated. The combined transformation rate of EE2 (0.057 h −1 ) in the presence of natural organic matter (NOM) and horseradish peroxidase (HRP) under simulated sunlight irradiation was markedly faster than that in the presence of NOM only (0.032 h −1 ). Similar pattern was also observed in real water matrix sampled from Taihu Lake. Further study revealed that the photodegradation and enzymatic transformation of EE2 were dramatically affected by NOM concentrations ranging from 0 to 20 mgC L −1 . NOM was found to invariably accelerate the photodegradation of EE2 with increasing concentration. On the contrary, the transformation rate of EE2 mediated by HRP was decreased along with the increase of NOM concentration. The reason may be that HRP was prone to be inactivated in solution with high NOM concentration. The transformation experiment of EE2 at ambient level under sunlight confirmed the significant contribution of HRP to the degradation of EE2 in the presence of NOM. The results indicated that oxidation mediated by HRP was an essential fate of EE2 and other congener contaminants in aquatic environment.

One-pot sequential asymmetric catalytic reactions as demonstrated in Table 1 represent one of the simplest kinds of enzymatic multiple-step catalytic processes. Yet quantitative analysis in these processes is more complicated than that in single-step kinetic resolutions or desymmetrization reactions, leading to lacking of a simple procedure for handling the kinetics in practical applications. Therefore based on the classification of substrate type and enzyme stereopreference for each reaction step, a thorough kinetic analysis for obtaining the analytical solution in each classification is carried out, with which the sufficient condition as an index for assessing an effective asymmetric enzymatic process is proposed. Case studies of monitoring the previous experimental data via the analytical solution and for fulfilling an assigned target for the intermediate or product are also addressed, showing the validity of the present analysis for the handling of kinetics in practical applications.

One essential engineering problem when developing an industrial enzymatic process concerns the choice of the reactor operating alternative based on a-priori knowledge of the process kinetics and enzyme inactivation characteristics. For a multi-enzymatic system, involving complex interactions among enzymes that exhibit optimal activity on different parametric domains, and a high-order deactivation, this problem requires an extended analysis. The optimization and control engineering problems become very challenging due to the process high nonlinearity and the presence of a large number of complex constraints. All these will translate into a multi-objective optimization problem to be solved for each case. An elegant option developed in this paper is to obtain sets of Pareto optimal solutions, also called Pareto-optimal fronts, successively generated for pairs of adverse objectives. Then, the final choice of the enzymatic reactor operating policy results from the comparative analysis of these Pareto-fronts. Exemplification is made for the complex case of the oxidation of D-glucose (DG) to 2-keto- d -glucose (kDG) in the presence of P2Ox (Pyranose oxidase, EC 1.1.3.10) and catalase, continuously operated in a three-phase mechanically agitated semibatch reactor (MASCR) with co-immobilized enzymes on alginate beads. Optimal operating policy choice is based on the minimum amount of required P2Ox that ensures an imposed reaction conversion and maximum reactor productivity under various technological constraints, and for catalase/P2Ox ratios of 200–300 U/U.

Leather processing involves many sequential steps from raw hide to the finished leather. All these steps have definite role on the quality of leather in order to produce a superior end product with affable properties. Several chemicals are being employed in these process steps. Many of these have been identified now as hazardous, harmful or atleast pose difficulties in treatment. Enzymes are being extensively used in many of these process steps as eco benign alternatives either replacing the chemicals completely or at least partly substituting them. In this study, an attempt has been made to achieve fibre opening using galactosidases from Aspergillus terreus replacing conventional lime. The standardized experiment showed that the leather obtained comparable to the traditionally produced leathers in terms of physical, bulk and functional properties. The developed enzymatic process of fibre opening showed remarkable reduction of effluent load such as Chemical Oxygen Demand and Total Dissolved Solids. The new method also entails substantial saving in process duration. Analysis of extent of interfibrillary material removal, scanning electron microscopy and histology studies corroborated visual observations of fibre opening. This process can be adopted in leather industry for greener and benign mode of application with environmental excellence.

The use of coconut fiber mature, green coconut shell, mature coconut shell and cactus is an important alternative as substrates for bioethanol production, since these lignocellulosic materials (LCMs) are abundant in Brazil, mainly in the Northeast Region. The first objective of this work was to evaluate the autohydrolysis pretreatment (AP) on these LCMs and the susceptibility of the treated materials to enzymatic hydrolysis (EH). The second part of the work deals with the application of semi-simultaneous saccharification and fermentation (SSSF) and simultaneous saccharification and fermentation (SSF) using Zymomonas mobilis, Pichia stipitis, Saccharomyces cerevisiae and as substrate the green coconut shell (selected according to the results obtained in the first part of the work). The LCMs after AP using the highest severity factor (4.64) showed changes in the chemical composition in comparison to the untreated LCMs: between the LCMs the cellulose increase was 48.55%, the hemicellulose decrease was 76.77% and an increase of 62.26% was observed for lignin. The green coconut shell was characterized by SEM, X-ray and FTIR after AP and its EH conversion into glucose was 92.52%. The best results on ethanol yield (90.09%) and ethanol productivity (0.21 g/(L h)) from green coconut shell were obtained by S. cerevisiae using SSSF. Overall, an efficient process for the bioethanol production from green coconut shell was developed., Brazilian research funding agencies CNPq (Proc:470356/2011-1) and CAPES (Proc:BEX5951/11-9).

The synthesis of biodiesel from sunflower oil and methanol based on transesterification using the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL-IM) has been investigated under silent conditions and under an ultrasound field. Ultrasound assisted process led to reduced processing time and requirement of lower enzyme dosage. We found for the first time that ratio 1:3 (oil to methanol) was favoured for the ultrasound assisted enzymatic process which is lower as that favoured for the silent process (ratio of 1.4). Our results indicate that intensification provided by ultrasound suppresses the need of the excess of the methanol reactant during the enzymatic biodiesel production. Ultrasound assisted enzymatic biodiesel production is therefore a faster and a cleaner processes., The authors acknowledge Brenntag India Pvt. Ltd. for kindly providing gift sample of lipase enzyme Lipozyme TL IM to carry out the research work. All authors acknowledge the funding of Department of Science and Technology and Portuguese Science Foundation under the Indo-Portuguese collaborative program.

The p53 signaling pathway plays critical roles in determining the radio-sensitivity of normal tissues but is frequently inactivated in cancer. In various cancer cells, p53 has different effects on radio-sensitivity through complex mechanisms. Acetylation of p53 is an important means of post-translational modifications and is indispensable for its activation that is a reversible enzymatic process. Both acetylation and deacetylation of p53 are involved in the fine regulation of cellular responses to DNA damage and genotoxic stress, such as radiation. Targeting the acetylation of p53 may enable the modulation of radio-sensitivity of cancer cells.

This study was carried out to assess physicochemical (color, moisture, protein and fat content) and rheological properties (fracture stress, fracture strain, degree of solidity and stress decay), as well as to assess the authenticity (using SDS-PAGE) of Minas Frescal cheese in 21 commercial samples acquired in Southern Brazil. Large differences among the samples, which tended to present a yellowish white color were observed. Moisture and protein influenced on the rheological properties and cheeses showed a tendency to being viscous and firm. SDS-PAGE revealed a wide unexpected variability in their proteins profiles and a densitometric casein/β-lactoglobulin ratio allowed to distinguish authentic cheese from adulterated ones. The profiles suggest the irregular presence of whey in the composition of these products, contrary to the enzymatic process legally required. These results emphasize the need for a more effective control, mainly in the selection of raw material, aiming to offer consumers authentic products.

Pretanning operation is always a challenging task in leather processes due to high generation of solid waste. Cleaner leather processing is a new avenue to exterminate the existing pollution complications. Enzymes are the best alternate to conventional chemicals in the context of cleaner leather processing. In the current investigation, pretanning processes are carried out with enzymes. Protease is used for unhairing and amylase is used to remove inter-fibrillary materials by treating with skin/hide matrix. Protease and amylase are suitably formulated (fibrozyme) and applied as a single system to substitute conventional liming/reliming processes. Fibrozyme with a concentration of 3.5% is optimized by drum method. Unhairing efficiency, extent of fibre opening through pore size evaluation, pollution load, morphology features evaluated through staining and SEM (Scanning Electron Microscope), physical strength characteristics, organoleptic properties and visual assessment of crust leathers are assessed. Unhairing efficiency of fibrozyme has matched with conventional liming system in terms of hair removal and general appearances. Shrinkage temperature of about 112 °C was observed in enzyme treated wet blue leathers. The physical strength of the crust leathers has met the UNIDO norms. Scanning electron microscopy study substantiates no distortion of fibres. The fibres are compact and uniformly opened up as well as distributed in enzymatic process. In single step enzyme process, there is reduction in pollution load. The study implies the role of enzyme in tanning industry and gives a new bioresource avenue to the existing cleaner processing systems.

A rectangular recycling photo-bioreactor using glucose oxidase (GOx) immobilized on TiO2/polyurethane (PU) was developed as a novel coupling of photodegradation and enzymatic process. This method was tested for removal of Acid Orange 7 (AO7), as a model pollutant. High efficiency of decolorization (>99%) was achieved after 22 min using the GOx/TiO2/PU photo-biocatalyst. Roles of various processes including photodegradation (TiO2/PU), enzymatic process (GOx/PU) and a coupling of photocatalytic–enzymatic (GOx/TiO2/PU) process were investigated in the presence and absence of UV light. All the experiments were performed in a circulation photoreactor equipped with a 6 W UV lamp with rate of 5 mL/min.

Research works on ecotechnologies (plasma treatments) or biotechnologies (enzymatic treatments) are being developed to substitute the alkaline soda process used to improve hydrophilicity of polyester fibres. Environmental impact assessment is necessary to validate these new strategies. Partial “gate to gate” LCA was used to compare three hydrophilisation processes: 1- chemical using sodium hydroxide, 2-air atmospheric plasma and 3- lipase enzyme based process. Laboratory experiments were carried to determine input and output data flows for optimum hydrophilic treatment of a particular polyester (PET) fabric using the three different processes. The functional unit was defined as “treatment of 1 kg of polyester fabric to achieve specific hydrophilic properties, measured by values of water contact angle and capillary uptakes. Generic and specific data bases were also used to determine flows, and the ReCiPe method used to convert all flows into environmental impacts. The energy related impact categories (“Ionising radiation”, “Climate change”, and “Fossil depletion values”) are the highest for all three processes, but air plasma treatment seems to be the most favourable for all impacts. For the enzymatic process, though very high degree of hydrophilisation can be reached compared to the soda treatment, higher environmental impacts are due to energy demanding enzyme deactivation process used. Partial LCA seems an interesting tool to assess process impacts at research stage, and to reorientate future research works.

A novel chemo-enzymatic synthesis of (S)-rivastigmine using ketoreductases with NADH/NADPH as the proton donor has been demonstrated. An exclusive enzymatic process has been developed by exploring the possible ketoreductases by screening to identify enzymes useful for the preparation of the (S)-isomer intermediate, and scaling up of the enzymatic process for the production of an adequate, enantiomerically pure precursor of rivastigmine and for the total synthesis of (S)-rivastigmine.

A mathematical model has been developed for an enzymatic process with kinetically controlled synthesis. Model reduction and detailed system analysis have been undertaken to examine the main properties of this enzyme reaction system. Optimal experimental design (OED) is developed to obtain the experimental conditions that will generate the most informative measurement data for parameter estimation. Both single-input and multiple-inputs optimisation strategies have been investigated to determine the best intensity levels of control inputs. The results demonstrate that parameter estimation quality can be improved through proper model-based experimental design.

t-Butanol was an excellent reaction medium for enzyme-mediated esterification of oleic acid with glycerol for 1,3-diolein preparation which has been proved by our group. Herein, to achieve the rational synthesis of 1,3-diolien, response surface methodology was applied to examine the effects of the significant variables and their reciprocal effects on the product synthesis. Under the optimal conditions (62.4°C, 0.75g Novozym 435, substrate molar ratio (oleic acid/glycerol) 2.4 and 4.8g t-butanol), the diolein yield of 87.4% could be achieved, and the value of 1,3-diolien/diolein was as high as 87.8%, which were quite close to the predicted values. Compared with the results of our previous single factor experiment, although the values of diolein yield and 1,3-diolien/diolein could not be improved markedly, the enzyme dosage and the reaction medium were spared by 25% and 20%, respectively, which was a remarkable improvement of the enzymatic process.

Design and optimal operation of an enzymatic process depend on the characteristics of the free- vs. immobilized-enzyme, purification problems, materials and operation costs. When the enzyme stabilization is not fully successful, the optimal choice of the reactor type and operation mode is depending on the process and enzyme deactivation characteristics. Quick simulation of operation modes based on the process kinetics and a library of reactor models can help in comparing alternatives for getting the final decision. The analysis is exemplified for two enzymatic processes, by determining the optimal operating policy for several tested reactors: classic batch, batch with intermittent addition of enzyme, semi-batch reactor, continuously operated packed-bed column, or a mechanically agitated reactor with immobilized enzyme in small beads. Prediction of reactor performances points out the best choice for the given enzyme characteristics, and also conditions allowing to switch the production from large-volume batches to the continuous operation mode.

Stevioside is a natural sweetener extracted from leaves of Stevia rebaudiana Bertoni, which is commercially produced by conventional (chemical/physical) processes. This article gives an overview of the stevioside structure, various analysis technique, new technologies required and the advances achieved in recent years. An enzymatic process is established, by which the maximum efficacy and benefit of the process can be achieved. The efficiency of the enzymatic process is quite comparable to that of other physical and chemical methods. Finally, we believe that in the future, the enzyme-based extraction will ensure more cost-effective availability of stevioside, thus assisting in the development of more food-based applications.

A series of O-alkyl derivatives of cyclodextrin: heksakis[2,3,6-tri-O-(2'-methoxyethyl)]-alpha-cyclodextrin; heksakis(2,3-di-O-methyl)-alpha-cyclodextrin; heptakis(2,3-di-O-methyl)-beta-cyclodextrin; heksakis[2,3-di-O-methyl-6-O-(2'-methoxyethyl)]-alpha-cyclodextrin; heptakis[2,3-di-O-methyl-6-O-(2'-methoxyethyl)]-beta-cyclodextrin; heksakis[2,3-di-O-(2'-methoxyethyl)]-alpha-cyclodextrin and heptakis[2,3-di-O-(2'-methoxyethyl)]-beta-cyclodextrin have been synthesized. Purity and composition of the obtained substances were examined. The cyclodextrin derivatives listed above as well as (2-hydroxypropyl)-alpha-cyclodextrin and (2-hydroxypropyl)-beta-cyclodextrin, the two commercially available ones, have been investigated as the additives in the course of enzymatic decomposition of L-tryptophan by L-tryptophan indole-lyase. It has been found that each of cyclodextrin derivatives causes the inhibition of enzymatic process, both competitive and non-competitive. The competitive inhibition is connected with the formation of inclusion complexes between cyclodextrins and L-tryptophan, related to the geometry of these complexes. The mechanism of the non-competitive inhibition is not so evident; it could be related to the formation of the cyclodextrin complexes on the surface of the enzyme, leading to the change in the flexibility of the enzyme molecule.

The kinetic resolution of 1-chloro-3-[4-(2-methoxyethyl)phenoxy]-2-propanol rac-4 with Novozym 435 and vinyl stearate, a key step in the gram-scale synthesis of (2S)-2-[[(2R)-2-hydroxy-3-[4-(2-methoxyethyl)phenoxy]propyl]amino]-1-butanol (R,S)-1 a potent antihypertensive agent currently under investigation, is reported here. Our approach differs from the previously reported synthesis, which involves a tedious and poorly effective fractional crystallization of (R,S)-1. This novel approach incorporates an enzymatic resolution for the efficient preparation of the oxirane precursor (R)-3. The two main advantages arising from this strategy are the high enantioselectivity of the enzymatic process and the facilitated recovery of the hydrophobic stearate intermediate (S)-5.

A novel host cell posttranslational modification system, termed sumoylation, has recently been characterized. Sumoylation is an enzymatic process that is biochemically analogous to, but functionally distinct from, ubiquitinylation. As in ubiquitinylation, sumoylation involves the covalent attachment of a small protein moiety, SUMO, to substrate proteins. However, conjugation of SUMO does not typically lead to degradation of the substrate and instead has a more diverse array of effects on substrate function. As the list of sumoylation substrates has expanded, a common theme is that many substrates exhibit sumoylation-dependent subcellular distribution. While the molecular mechanisms by which sumoylation targets protein localization are still poorly understood, it is clear that this modification system is an important regulator of intracellular protein localization, particularly involving nuclear uptake and punctate intranuclear accumulation.

The lipase-catalyzed kinetic resolution of the racemic γ-hydroxy ester 2 , coupled with subsequent acid-mediated cyclization, is an effective method for the synthesis of both enantiomers of β-benzyl-γ-butyrolactone 1 . This enzymatic process affords the product with high enantiomeric excess under mild reaction conditions and does not require optically active starting materials.

Summary The existence of a flux of proton donors from skin (inner part of the forearm) to the electrode was observed in 12 male and female volunteers. This flux was used to collect and identify the ionic species responsible for skin acidity. It was then found that: (i) pK of these proton donors (pK = 6.13 ± 0.07) was quasi-identical to that of trans -urocanic acid (6.10), and (ii) the amount of urocanic acid present in stratum corneum was sufficient in itself to explain the acidic level as measured with pH meter (R = 0.8484, n=10, p=0.00136). As a result, the contribution of other ionic species can be considered as negligible in normal human skin. The data recorded led us to identify three groups (Fast, Medium, and Slow) characterized by different skin surface pH values (low, medium, and close to neutral) and showing a pH gradient in the outer layers of the stratum corneum, or not. Data analysis suggests that these characteristics depend on urocanic acid production rate within the stratum corneum and that this production rate is self-regulated by its urocanic acid content.

Chiral 1,3-oxazolidine-2-thiones were prepared in enantiopure form from renewable resources through an enzymatic process involving immobilized myrosinase (thioglucoside glucohydrolase E.C. 3.2.3.1).

Three decades ago Martin Karplus's group performed the first molecular dynamics simulations of trypsin in order to address the transition from the zymogen to its active form. Based on the low computational power existing at that time only high frequency fluctuations could be observed, but not the full transition, were observed. By performing accelerated molecular dynamics (aMD) simulations, a very promising approach to increase the configurational sampling of atomistic simulations, we were able to observe the amino tail insertion into the conserved hydrophobic pocket, a crucial step of the transition mechanism. The results allow us to address a very important enzymatic process, providing new evidence about the underlying thermodynamics.

dl -Phenylhydantoin can be converted into d -phenylglycine by an enzymatic process. d -phenylglycine is an important starting material in the production of β-lactams such as semisynthetic penicillins and cephalosporins. In our laboratory, the synthesis of phenylhydantoin was achieved from hydantoin and cyclohexanone in the presence of a base. An efficient and fast isocratic reversed-phase high-performance liquid chromatography method was developed for the determination of phenylhydantoin, cyclohexylhydantoin and cyclohexylidenehydantoin. Quantitative analysis was carried out by an external standard method.

Multigram quantities of the title compounds in their enantiomerically-pure forms have been prepared by employing a chiral precursor which can be obtained via a facile enzymatic process.

A tofu product was fabricated from faba beans (Vicia Faba L. Minor). Various experimental conditions were modified to optimize product yield and organoleptic properties. Optimum yield (66.8% by weight and 44.8% protein) of the faba bean tofu was obtained with bean to water ratio of 1:10 by the decantation process. Increasing amounts of ascorbic acid increased the protein content and texture firmness and lowered the grey coloration of the product. Colour intensity may further be decreased by removing the cuticle before grinding. Also, increasing amounts of coagulant decreased the protein yield. Glucono-δ-lactone gave a tofu of very pale colour, but the protein yield was less than the other salts. The optimized decantation process gave better yield than the enzymatic process, and the resulting products were of similar texture and firmness as the tofu made from soya.

The structural requirements of the Asn-X-Thr(Ser) sequence for the N-glycosylation of proteins has been traced to a local conformation acting as a signal for the enzymatic process. The conformational space of the smallest in vivoN-glycosylation substrate, Ac-Asn-Ala-Thr-NH2, has been thoroughly explored using energy calculations. All the lowest energy conformers have been characterized as bended structures.

The curves of the time ( t ) dependent product (Pr) accumulation for Monod, Wyman & Changeux model (1965) , where the rate of installation of equilibrium between two conformational states of oligomeric enzyme (R ⇄ T) is comparable to that of enzymatic process, are theoretically analysed. It is assumed that the complexes of R and T forms are in rapid equilibrium with the free components. The character of the effective rate constant of conformational transition R ⇄ T and the value of τ (where τ is the intercept of the linear part of the kinetic curve of [Pr] versus t with the time axis) versus the substrate concentration is analysed. It is also shown that slow conformational transition R ⇄ T can be manifested by an unusual shape for Monod et al. model plots of initial velocity of the enzyme reaction v . the substrate concentration (these curves can clearly display expressed inflection points and Hill's cooperativity coefficient less than unity).

From analysis of spectral and kinetic parameters of firefly luciferin-luciferase system, a kinetic scheme for the enzymatic process is proposed and discussed. The allosteric regulation of luciferase catalytic activity by ATP and its analogs is considered. Choline-containing phospholipids are shown to be specific luciferase activators. Some properties of firefly luciferase and the luciferase synthesized during mRNA translation in frog oocytes are compared.

Porcine pancreatic lipase in anhydrous organic solvents catalyses the lactonisation of a number of esters of γ-hydroxyacids in nearly quantitative yields. This enzymatic process was used for the highly stereoselective synthesis of (S)-(−)-γ-methylbutyrolactone, (R)-(+)-γ-methylbutyrolactone and of optically active γ-phenylbutyrolactone.

The repair of sublethal freeze-thaw damage has been demonstrated by exposing cells to two freeze-thaw cycles separated by various times at 37 °C. The influence of suboptimal temperatures and hypoxia on this repair process was investigated. Repair was found to be temperature sensitive, decreasing as the temperature was lowered from 37 °C, and was virtually nonexistent at 5 °C. Lowering the oxygen concentration in the medium to 6.6 μ M or to 0.66 μ M had no significant effect on repair. The repair system then appears to involve an enzymatic process which is not greatly dependent on the oxygen concentration in the range of 277 (aerobic) to 0.66 μ M O 2 in the medium.

Summary Activity of erythrocyte acetylcholinesterase at low ionic strength. In the absence of added ions other than acetylcholine chloride used as substrate, Lineweaver-Burk plots of partially purified bovine erythrocyte acetylcholinesterase (EC 3.1.1.7) and of human erythrocyte membrane-bound acetylcholinesterase present a negatively concave curvature in the region of moderate substrate concentrations. This curvature which indicates an activation of the enzymatic process is interpreted as being due to the binding of a second substrate molecule at a peripheral acetylcholinesterase site.

When d-amino acid oxidase (d-amino acid:O2 oxidoreductase (deaminating), EC 1.4.3.3) is treated with NaBH4 during the enzymatic reaction, the carbon moiety resulting from the deamination of the substrate is bound to the e-NH2 of lysine residues of the enzyme. The isolation of several peptides containing these “reactive” lysine residues is described. Their characteristics are discussed, regarding the possible role of a particular lysine residue in the enzymatic process.

After Raper (1) traced the series of chemical steps by which tyrosine is oxidized to melanin by non-mammalian tyrosinases (Fig. 1) there appeared reports about various chemical substances that inhibit this reaction at different stages through various mechanisms. These reports have recently been reviewed by Lerner and Fitzpatrick (2). The present study deals with the mode of action of some chemical agents that modify the melanin formation brought about by mammalian tyrosinase. This investigation was undertaken in connection with a search for substances which would be taken up selectively in melanoblasts by combining with intermediates in the enzymatic process of tyrosine oxidation to form a precipitate. If such substances could be found it would make possible the selective destruction of melanin-forming neoplastic cells.