Search

Abstract Our research explores the detrimental effects of microplastic (MP) exposure on adipose tissue aging and function, emphasizing the potential health risks associated with environmental pollutants. Utilizing both in vivo and in vitro models, we discovered that MPs accumulate in adipose tissues, leading to cellular senescence, inflammation, and hindered adipogenic differentiation. Notably, our findings demonstrate that MPs prompt an aging response in both epididymal and inguinal white adipose tissue, increase senescence-associated β-galactosidase activity, and upregulate key senescence and inflammatory markers. Furthermore, we show that MPs disrupt normal adipogenic differentiation by reducing lipid droplet formation and downregulating critical adipogenic markers. These insights highlight the urgent need for further investigation into the long-term consequences of MP pollution on biological aging and underscore the importance of developing public health strategies to mitigate these effects.

This study represents the first report of the complete mitochondrial genome of a carnivorous stag beetle, Figulus punctatus. The genome is 17,664 bp long with a total of 37 genes including 13 protein-coding genes, 22 tRNA, and 2 rRNA. The nucleotide composition is 37.25% A, 31.71% T, 10.00% G, and 20.99% C (GC contents 30.99%). Our molecular phylogenetic analysis based on the maximum-likelihood method recognizes Figulini and Nigidiini as a monophyletic clade, with a robust support value, and suggests that their carnivorous feeding trait may have evolved once within the family.

For an ongoing systematic study of Korean Vespidae, we analyzed the complete mitochondrial genome of a social wasp, Vespula rufa (Linnaeus 1758), from the South Korea. The mitogenome is 17,521 bp in length, comprising 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes. The nucleotide composition is 40.5% adenines, 43.0% thymines, 6.0% guanines, and 10.5% cytosines. The GC content is 16.5%. A maximum-likelihood analysis was conducted to understand phylogenetic relationships, based on 13 complete mitogenome sequences of Vespinae species. We recognized that V. rufa is being placed basal within the genus Vespula. The complete mitochondrial genome of V. rufa provides useful genetic information for further studies.

The present study is aimed to report on Zimmermannia as new to Korean insect fauna including three species: Z. admiranda (Puplesis, 1984), Z. amani (Svensson, 1966), and Z. sivickisi (Puplesis, 1984). The redescription and images of adult and genitalia for each species are provided with an identification key to the Korean Zimmermannia. DNA barcode of each species is uploaded to the NCBI.

Euderomphalini Shafee, Rizvi and Khan (Hymenoptera: Eulophidae) is newly recognized from South Korea based on Euderomphale stomale Narendran and Hayat. The present study is to report the species as the first record in the country and to give a redescription along with the images of the diagnostic characteristics.

The rapid aging of the population worldwide presents a significant social and economic challenge, particularly due to osteoporotic fractures, primarily resulting from an imbalance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. While conventional therapies offer benefits, they also present limitations and a range of adverse effects. This study explores the protective impact of Neorhodomela munita ethanol extract (EN) on osteoporosis by modulating critical pathways in osteoclastogenesis and apoptosis. Raw264.7 cells and Saos-2 cells were used for in vitro osteoclast and osteoblast models, respectively. By utilizing various in vitro methods to detect osteoclast differentiation/activation and osteoblast death, it was demonstrated that the EN’s potential to inhibit RANKL induced osteoclast formation and activation by targeting the MAPKs-NFATc1/c-Fos pathway and reducing H2O2-induced cell death through the downregulation of apoptotic signals. This study highlights the potential benefits of EN for osteoporosis and suggests that EN is a promising natural alternative to traditional treatments.

It has been reported that the essential oil extracted from Abies koreana has skin-improving activity, such as anti-wrinkle and whitening effect. However, the key ingredients that facilitate such biological activity has not been fully elucidated. In the present study, to identify the key skin-improving component(s) of the A. koreana essential oil, 10 sequentially fractioned essential oil from A. koreana pine by hydrodistillation were examined for their effect on tyrosinase activity. Out of 10 fractions, only 1 fraction significantly suppressed tyrosinase activity, and subsequent GC/MS analysis indicated that borneol and its acetate ester, bornyl acetate, were unique to the effective fraction, suggesting they are responsible for the skin-improving activity of the essential oil from A. koreana. The biological activity of borneol was evaluated, and borneol significantly inhibited ultraviolet irradiation-induced tyrosinase and matrix metalloproteinase 1 activity while maintain collagen type I synthesis. The results of this study suggest that borneol is a key component of A. koreana essential oil that has potential for mediating whitening and anti-wrinkle effects.

The genus Ericydnus in Encyrtidae is newly recognized with three species from South Korea: E. huangi, E. infuscatus, and E. longicornis. A key to Korean species, diagnoses and diagnostic characters are presented along with images of the species. In addition, new Korean names are given for the three species.

Adipose-derived mesenchymal stem cells (ASCs) have the potential to differentiate into bone, cartilage, fat, and neural cells and promote tissue regeneration and healing. It is known that they can have variable responses to hypoxic conditions. In the present study, we aimed to explore diverse changes in the cells and secretome of ASCs under a hypoxic environment over time and to present the possibility of ASCs as therapeutic agents from a different perspective. The expression differences of proteins between normoxic and hypoxic conditions (6, 12, or 24 h) were specifically investigated in human ASCs using 2-DE combined with MALDI-TOF MS analysis, and secreted proteins in ASC-derived conditioned media (ASC-derived CM) were examined by an adipokine array. In addition, genetic and/or proteomic interactions were assessed using a DAVID and miRNet functional annotation bioinformatics analysis. We found that 64 and 5 proteins were differentially expressed in hypoxic ASCs and in hypoxic ASC-derived CM, respectively. Moreover, 7 proteins among the 64 markedly changed spots in hypoxic ASCs were associated with bone-related diseases. We found that two proteins, cathepsin D (CTSD) and cathepsin L (CTSL), identified through an adipokine array independently exhibited significant efficacy in promoting osteocyte differentiation in bone-marrow-derived mesenchymal stem cells (BM-MSCs). This finding introduces a promising avenue for utilizing hypoxia-preconditioned ASC-derived CM as a potential therapeutic approach for bone-related diseases.

Parasitic moths are common in social wasp (Hymenoptera) nests, attacking many species of Polistinae and a few species of Vespinae. In the Republic of Korea, two moth species are known to parasitize the brood of Polistes rothneyi koreanus: Pyralis regalis (Pyralidae) and Anatrachyntis japonica (Cosmopterigidae). Although previously reported elsewhere, a novel case of parasitization was recently documented in the Republic of Korea, in which Hypsopygia mauritialis (Pyralidae) was identified in the nests of social wasps. Pyralis regalis is the most common parasitic moth in the Republic of Korea, feeding on the nests of 11 species of social wasps, mostly the Korean Vespa species. To that list of hosts, we add a species of Dolichovespula and two species of Polistes. Parasitism of Vespa velutina nigrithorax, an invasive alien hornet, by both P. regalis and H. mauritialis, was observed for the first time. However, their potential to control invasive alien hornets is expected to be low. This study provides new insights into the diversity of nest-parasitic moths in social wasp nests and their hosts in the Republic of Korea, and highlights the potential for these moths to impact pest populations.

In this study, the genus Eugahania (Hymenoptera: Chalcidoidea: Encyrtidae) and its three species E. flaviscapus, E. latiscapus, and E. yanoi are newly discovered from the Korean Peninsula. The morphological information with photographs of the three species is presented.

Osteoarthritis: Drug-induced stem cell differentiation shows therapeutic promise A novel method of generating healthy cartilage cells from stem cells could repair and regenerate joints and bones damaged by osteoarthritis. The cells that produce and maintain cartilage tissue are known as chondrocytes. Stem cell therapy could potentially re-start cartilage and bone regeneration in patients with osteoarthritis, however scientists have struggled to successfully induce stem cells to differentiate into functioning chondrocytes. A new method developed by Soyeon Lim and Ki-Chul Hwang at the Catholic Kwandong University, Gangneung, South Korea, and co-workers uses a drug called ellipticine to boost the expression of Sox-9, a key protein involved in cartilage development. The researchers found that the ellipticine-based method induced a mature, healthy chondrocyte population in cell cultures and rat models of osteoarthritis. Rats injected with these cells recovered from cartilage damage, suggesting a potential osteoarthritis therapy.

Cardiovascular diseases have been leading cause of death worldwide for many decades, and obesity has been acknowledged as a risk factor for cardiovascular diseases. In the present review, human epicardial adipose tissue-derived miRNAs reported to be differentially expressed under pathologic conditions are discussed and summarized. The results of the literature review indicate that some of the epicardial adipose tissue-derived miRNAs are believed to be cardioprotective, while some others show quite the opposite effects depending on the underlying pathologic conditions. Furthermore, they suggest that that the epicardial adipose tissue-derived miRNAs have great potential as both a diagnostic and therapeutic modality. Nevertheless, mainly due to highly limited availability of human samples, it is very difficult to make any generalized claims on a given miRNA in terms of its overall impact on the cardiovascular system. Therefore, further functional investigation of a given miRNA including, but not limited to, the study of its dose effect, off-target effects, and potential toxicity is required. We hope that this review can provide novel insights to transform our current knowledge on epicardial adipose tissue-derived miRNAs into clinically viable therapeutic strategies for preventing and treating cardiovascular diseases.

Vascular calcification (VC) and osteoporosis are age-related diseases and significant risk factors for the mortality of elderly. VC and osteoporosis may share common risk factors such as renin-angiotensin system (RAS)-related hypertension. In fact, inhibitors of RAS pathway, such as angiotensin type 1 receptor blockers (ARBs), improved both vascular calcification and hip fracture in elderly. However, a sex-dependent discrepancy in the responsiveness to ARB treatment in hip fracture was observed, possibly due to the estrogen deficiency in older women, suggesting that blocking the angiotensin signaling pathway may not be effective to suppress bone resorption, especially if an individual has underlying osteoclast activating conditions such as estrogen deficiency. Therefore, it has its own significance to find alternative modality for inhibiting both vascular calcification and osteoporosis by directly targeting osteoclast activation to circumvent the shortcoming of ARBs in preventing bone resorption in estrogen deficient individuals. In the present study, a natural compound library was screened to find chemical agents that are effective in preventing both calcium deposition in vascular smooth muscle cells (vSMCs) and activation of osteoclast using experimental methods such as Alizarin red staining and Tartrate-resistant acid phosphatase staining. According to our data, citreoviridin (CIT) has both an anti-VC effect and anti-osteoclastic effect in vSMCs and in Raw 264.7 cells, respectively, suggesting its potential as an effective therapeutic agent for both VC and osteoporosis.

The complete mitochondrial genome of carnivorous Nigidius miwai was analyzed prior to a study on evolution of carnivorous pathway within the family. This species’ genome had a total length of 18,462 bp (GenBank accession number: OL597607), comprising 36 genes along with 13 protein-coding genes, 21 tRNA genes, two rRNA genes, and an A + T rich region. The nucleotide composition was 37.2% A, 33.8% T, 9.2% G, and 19.8% C (GC contents 29.0%). The phylogenetic tree indicated that N. miwai is a distinctive species within Nigidiini of Lucaninae.

A small-scale grid-connected PV system that is easy to install and is inexpensive as a remote monitoring system may cause economic losses if its failure is not found and it is left unattended for a long time. Thus, in this study, we developed a low-cost fault detection remote monitoring system for small-scale grid-connected PV systems. This active monitoring system equipped with a simulation-based fault detection algorithm accurately predicts AC power under normal operating conditions and notifies its failure when the measured power is abnormally low. In order to lower the cost, we used a single board computer (SBC) with edge computing as a data server and designed a monitoring system using openHAB, an open-source software. Additionally, we used the Shewhart control chart as a fault detection criterion and the ratio between the measured and predicted ac power for the normal operation data as an observation. As a result of the verification test for the actual grid-connected PV system, it was confirmed that the developed remote monitoring system was able to accurately identify the system failures in real-time, such as open circuit, short circuit, partial shading, etc.

Melittobia acasta (Walker, 1839) had previously been found from a breeding facility of Bombus terrestris (Linnaeus, 1758), an imported pollinator in South Korea. M. acasta was newly found parasitizing Sceliphron camentarium (Drury, 1773) of Sphecidae, a wild host species, in the country. Brief biological information of the parasitoid is provided along with detailed images acquired from rearing. Descriptions and images of diagnostic characters of female and male as well are given. Keywords: Eulophidae, Melittobia acasta, New host record, Sceliphron camentarium, Sphecidae

Nidus vespae, commonly known as the wasp nest, has antioxidative, anti-inflammatory, antimicrobial, and antitumor properties. However, the anti-obesity effects of Nidus vespae extract (NV) have not yet been reported. This study aimed to elucidate the potential anti-obesity effects of NV in vivo and in vitro, using a high-fat diet (HFD)-induced obese mouse model and 3T3-L1 adipocytes, respectively. NV administration to HFD-induced obese mice significantly decreased the mass and plasma lipid content of adipose tissues. Uncoupling protein-1 expression was significantly higher in the inguinal white adipose tissues of NV-treated mice than in those of HFD-fed mice. Furthermore, we found that NV inhibited the differentiation and intracellular lipid accumulation of 3T3-L1 adipocytes by regulating the insulin signaling cascade, including protein kinase B, peroxisome proliferator-activated receptor gamma, CCAAT/enhancer binding protein alpha, and adiponectin. These findings suggest that NV may exhibit therapeutic effects against obesity by suppressing adipose tissue expansion and preadipocyte differentiation, thereby providing critical information for the development of new drugs for disease prevention and treatment. To our knowledge, this study provides the first evidence of the anti-obesity effects of NV.

Although the optimal therapy for myocardial infarction includes reperfusion to restore blood flow to the ischemic area, myocardial injury after ischemia/reperfusion usually leads to an inflammatory response, oxidative stress, and cardiomyocyte apoptosis. In this study, rat adipose-derived stem cells were differentiated into low-thermogenic beige adipocytes (LBACs) and high-thermogenic beige adipocytes (HBACs) to study the different cardioprotective effects of heterogeneous expression of brown adipocytes. We found that antioxidant and antiapoptotic factors in H9c2 cardiomyocytes were upregulated by high levels of secreted FGF21 in HBAC conditioned medium (HBAC-CM), whereas FGF21 in HBAC-CM did not affect antioxidative or antiapoptotic cell death in H9c2 cardiomyocytes with Nrf2 knockdown. These results show that NRF2 mediates antioxidative and antiapoptotic effects through the HBAC-secreted factor FGF21. Consistent with this finding, the expression of antioxidant and antiapoptotic genes was upregulated by highly secreted FGF21 after HBAC-CM treatment compared to LBAC-CM treatment in H9c2 cardiomyocytes via NRF2 activation. Furthermore, HBAC-CM significantly attenuated ischemic rat heart tissue injury via NRF2 activation. Based on these findings, we propose that HBAC-CM exerts beneficial effects in rat cardiac ischemia/reperfusion injury by modulating NRF2 and has potential as a promising therapeutic agent for myocardial infarction.

In the present study, we report two lepidopteran pests and their damage on the cones of Abies koreana E. H. Wilson from Mt. Halla, Jeju, South Korea: Cydia kamijoi Oku and Dioryctria abietella (Denis & Schiffermüller). The former is new to Korea, and the latter is well known as an insect pest on cones of various coniferous trees. Larvae of these species bore into the immature cones of the host tree. Damaged cones can be easily distinguished by reddish brown frass piled around the holes that were made by the moths, and the cones that are severely damaged become crooked and eventually are folded in half. The average damage rate on the cones was 75.3±2.34% from the survey sites in 2014, but the insect damage could not be found again from the sites as the host did not bear any cones in 2015. Descriptions and images of C. kamijoi and D. abietella are provided along with a list of host species and distribution.

Leluthia honshuensis Belokobylskij & Maeto, 2006 (Hymenoptera: Braconidae) was found as an ectoparasitoid of the first- and second-instar larvae of the Asian longhorned beetle (ALB), Anoplophora grabripennis (Motschulsky) (Coleoptera: Cerambycidae) from Gwangneung forest, Pocheon, Republic of Korea. This discovery was made during the investigation for parasitoids of ALB in 2016. We report here the first known host of Leluthia as the ALB. In addition, a diagnosis and detailed photographs of L. honshuensis are given. Images of the holotype specimen are also provided for comparison.

Spatial and temporal variation in ecological environments may result in spatial and temporal variation in communities. Temporal studies of biodiversity are essential for forecasting future changes in community structure and ecosystem function. Therefore, determining the mechanisms that drive temporal change in communities remains an important and interesting challenge in ecology. We quantified spatial and temporal variations in carabid beetle communities and site-specific environmental factors for 5 years at nine study sites on three mountains in the Baekdudaegan Mountain Range, Korea. Carabid beetle communities exhibited significant temporal variation, which was larger than spatial variations between and within mountains. Environmental factors mostly varied between sites within mountains. Community variation was only weakly associated with environmental factors at wide scales, i.e., between sites on three mountains, but was strongly associated at narrow spatial scales, i.e., between sites within one mountain. Our results indicate that temporal variation in communities occurs in response to variations in the local climate, and that the patterns of temporal variation differ between mountains. Thus, temporal surveys of insect communities and climates at local scales are important for predicting temporal changes in the communities.

Background/Aims: Stromal vascular fraction (SVF) cells are a mixed cell population, and their regenerative capacity has been validated in various therapeutic models. The purpose of this study was to investigate the regenerative mechanisms utilized by implanted SVF cells. Using an in vitro co-culture system, we sought to determine whether SVF implantation into impaired tissue affects endogenous mesenchymal stem cell (MSC) differentiation; MSCs can differentiate into a variety of cell types, and they have a strong regenerative capacity despite their low numbers in impaired tissue. Methods: Adipose-derived SVF cells obtained from four donors were co-cultured with bone marrow-derived MSCs, and the differential expression of osteogenic markers and osteogenic differentiation inducers over time was analyzed in mono-cultured MSCs and MSCs co-cultured with SVF cells. Results: The co-cultivation of MSCs with SVF cells significantly and mutually induced the expression of osteogenic-specific markers via paracrine and/or autocrine regulation but did not induce adipocyte, chondrocyte or myoblast marker expression. More surprisingly, subsequent osteogenesis and/or comparable effects were rapidly induced within 48 h. Conclusion: To the best of our knowledge, this is the first study in which osteogenesis and/or comparable effects were rapidly induced in bone marrow-derived MSCs and adipose-derived SVF cells through co-cultivation. Our findings suggest that the positive effects of SVF implantation into impaired bone may be attributed to the rapid induction of MSC osteogenesis, and the transplantation of co-cultured and preconditioned SVF cells and/or MSCs may be more effective than the transplantation of untreated cells for the treatment of bone defects.

The complete mitochondrial genome of a horntail wasp, Tremex fuscicornis, was analyzed prior to a systematic study on South Korean Siricidae. This species genome has a total length of 16,359 bp (GenBank accession number: MT425058), consisting of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and an A + T rich control region. The nucleotide composition is 41.8% T, 38.2% A, 14.3% C, and 5.7% G. The result of the maximum-likelihood analysis indicates that T. fuscicornis is a distinctive species in Siricidae, and this mitogenomic sequence can be used as a reference for phylogenetic studies on the superfamily Siricoidea.

We report the complete mitochondrial genome of Eudarcia gwangneungensis Roh & Byun, . The genome has a total length of 15,391 bp (GenBank accession number: MN413148), consisting of 13 protein-coding genes, 22 tRNA, 2 rRNA genes, and A + T-rich control region. The nucleotide composition was 39.4% T, 40.4% A, 12.7% C, and 7.4% G. This study is the first report of a complete mitochondrial genome of a meessiid species, and the mitogenomic sequence can be used as a reference data for extensive phylogenetic studies of Tineoidea.

Two species of Elasmus (Hymenoptera: Eulophidae) are newly recognized in South Korea: Elasmus japonicus Ashmead and Elasmus polistis Burks. They were reared from the nests of Polistes (Hymenoptera: Vespidae): E. japonicus from Polistes rothneyi koreanus and E. polistis from Polistes snelleni and P. rothneyi koreanus. Both species are biparental and usually have more females than males.

In the present study, we report the first complete mitochondrial DNA genome of the genus Callipogon based on C. relictus, a natural monument and endangered species in South Korea. The mitogenome is 15,742 base pairs with 13 protein coding genes (PCGs), two rRNAs, 22 tRNAs, and a 1033 bp long AT-rich region. The overall base composition was 67.3% AT and 32.7 GC. Among 13 PCGs, seven genes (Nad2, Atp8, Atp6, Nad4L, Nad6, Cob, Nad1) harbour the typical stop codon TAA or TAG, whereas remaining five genes terminate with T. Interestingly, Cox3 employs AGA as the termination codon.

Human adipose-derived stem cells (hASCs) can be isolated from fat tissue and have attracted interest for their potential therapeutic applications in metabolic disease. hASCs can be induced to undergo adipogenic differentiation in vitro by exposure to chemical agents or inductive growth factors. We investigated the effects and mechanism of differentiating hASC-derived white adipocytes into functional beige and brown adipocytes with isoliquiritigenin (ILG) treatment. Here, we showed that hASC-derived white adipocytes could promote brown adipogenesis by expressing both uncoupling protein 1 (UCP1) and PR/SET Domain 16 (PRDM16) following low-dose ILG treatments. ILG treatment of white adipocytes enhanced the expression of brown fat-specific markers, while the expression levels of c-Jun N-terminal kinase (JNK) signaling pathway proteins were downregulated. Furthermore, we showed that the inhibition of JNK phosphorylation contributed to white adipocyte differentiation into beige adipocytes, which was validated by the use of SP600125. We identified distinct regulatory effects of ILG dose responses and suggested that low-dose ILG induced the beige adipocyte potential of hASCs via JNK inhibition.

Objective Adipose-derived stromal vascular fractions (SVFs) are heterogeneous complex populations of cells with therapeutic efficacy for tissue generation and vascular stabilization. SVFs have cardiomyogenic potential, and many researchers have examined the possibility of SVF transplantation for heart disease. In cell-based therapies, donor age affects the regenerative capability, cell yield, and differentiation potential of adult tissues; however, opposing or controversial results have been found in humans. We examined whether SVF transplantation into impaired heart tissue shows differential effects according to donor age. Methods We investigated differences in protein expression in human umbilical vein endothelial cells (HUVECs) co-cultured with adipose-derived adherent stromal cells (ADASs) from donors of different ages [>40-year-olds (40s group) and >60-year-olds (60s group)] under oxidative stress conditions. Results Although co-culturing HUVECs with ADASs ameliorated inflammation due to increased oxidative stress conditions, few differences were observed between the ADASs from the 40s and 60s groups. Moreover, the Database for Annotation, Visualization, and Integrated Discovery classification tool revealed differentially expressed genes in the Kyoto Encyclopedia of Genes and Genomes pathway associated with cytokine–cytokine receptor interaction in response to ADASs. Conclusion Protein expression profiles were unchanged in HUVECs induced by isolated ADASs from donors of different ages under oxidative stress conditions.

In the present paper, we make a first report on the complete mitochondrial DNA genome of Leptaulax koreanus, a Korean endemic species, in Passalidae. The mitogenome is 18,730 base pairs with 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and a 4240 bp long AT-rich region. The overall base composition is 78.4% AT and 21.6% GC. The maximum likelihood analysis suggested that L. koreanus is a sister to other Scarabaeoidea species.

In order to identify the parasitoids of Phyllocnistis citrella Stainton [commonly known as the citrus leafminer (CLM)], we collected CLM larvae and pupae in the Seogwipo area of Jeju-do, identified parasitoid species, and determined parasitism rates. In May 2014, nine parasitoids were identified from the CLM larvae and pupae that infested 300 fresh citrus leaves, yielding a parasitism rate of 3.03%. In August 2014, 53 parasitoid wasps emerged from 203 collected CLM larvae and pupae, indicating that the parasitism rate rose to 25.84%. The parasitoid wasps observed in May 2014 consisted of five individuals of Sympiesis sp. 1 (Eulophidae), one Pnigalio sp. 1 (Eulophidae), and three Aphelinus sp. 1 (Aphelinidae). The highest proportion of the parasitic wasps that emerged in August 2014 were Sympiesis sp. 1 (n = 49), followed by Quadrastichus sp. 1 (Eulophidae; n = 4). This study documents the seasonal parasitism rate of parasitic wasps and basic characteristics of each parasitoid in Korea.

Lysine decarboxylase (LDC) is a crucial enzyme for acid stress resistance and is also utilized for the biosynthesis of cadaverine, a promising building block for bio-based polyamides. We determined the crystal structure of LDC from Selenomonas ruminantium (SrLDC). SrLDC functions as a dimer and each monomer consists of two distinct domains; a PLP-binding barrel domain and a sheet domain. We also determined the structure of SrLDC in complex with PLP and cadaverine and elucidated the binding mode of cofactor and substrate. Interestingly, compared with the apo-form of SrLDC, the SrLDC in complex with PLP and cadaverine showed a remarkable structural change at the PLP binding site. The PLP binding site of SrLDC contains the highly flexible loops with high b-factors and showed an open-closed conformational change upon the binding of PLP. In fact, SrLDC showed no LDC activity without PLP supplement, and we suggest that highly flexible PLP binding site results in low PLP affinity of SrLDC. In addition, other structurally homologous enzymes also contain the flexible PLP binding site, which indicates that high flexibility at the PLP binding site and low PLP affinity seems to be a common feature of these enzyme family.