Amino Acid Composition Analysis Research Articles

Characterization of Fish Skin Hydrolysates Exhibiting Dipeptidyl Peptidase IV Inhibitory Activity

Dipeptidyl peptidase IV (DPP-IV) inhibitors are antidiabetic drugs that can lower blood sugar levels. There are still few reports on the DPP-IV inhibitory activity of peptides obtained from discarded fish skin. Therefore, we prepared various enzymatic hydrolysates using the skins of six fish species and investigated their DPP-IV inhibitory effects. As a result, it was found that the DPP-IV inhibitory activity of yellowtail hydrolysate by Alcalase was higher than that of other enzymes. In addition, the IC50 after ethanol fractionation was found to be lower in yellowtail and eel skin hydrolysate. Amino acid composition analysis showed that the hydrolysate obtained from the skin of the yellowtail contained the highest amount of Gly, followed by Pro, Hyp, and Ala, indicating that it was a peptide derived from type I collagen. Fractionation with ethanol showed that the DPP-IV inhibitory components were contained in the low molecular weight fraction. The artificial digestion test observed no DPP-IV inhibitory activity or average molecular weight change. The DPP-IV inhibitory peptide obtained from fish skin has the potential to be applied as a food material to various food products.

One-step high efficiency separation of prolyl endopeptidase from Aspergillus niger and its application

Prolyl endopeptidase from Aspergillus niger (An-PEP) is an enzyme that recognizes C-terminal peptide bonds of amino acid chains and cleaves them by hydrolysis. An aqueous two-phase system (ATPS) was used to separate An-PEP from fermentation broth. Through single factor experiments, the ATPS containing 16 % (w/w) PEG2000 and 15 % (w/w) (NH4)2SO4 at pH 6.0 obtained the recovery of 79.74 ± 0.16 % and the purification coefficient of 7.64 ± 0.08. It was then used to produce soy protein isolate peptide (SPIP) by hydrolysis of soy protein isolate (SPI), and SPIP-Ferrous chelate (SPIP-Fe) was prepared with SPIP and Fe2+. The chelation conditions were optimized by RSM, as the chelation time was 30 min, chelation temperature was 25 °C, SPIP mass to VC mass was two to one and pH was 6.0. The obtained chelation rate was 82.56 ± 2.30 %. The change in the structures and functional features of SPIP before and after chelation were investigated. The FTIR and UV–Vis results indicated that the chelation of Fe2+ and SPIP depended mainly on the formation of amide bonds. The fluorescence, SEM and amino acid composition analysis results indicated that Fe2+ could induce and stabilize the surface conformation and change the amino acid distribution on the surfaces of SPIP. The chelation of SPIP and Fe2+ resulted in the enhancement of radical scavenging activities and ACE inhibitory activities. This work provided a new perspective for the further development of peptide-Fe chelates for iron supplement.

The potential benefits of Oreochromis mossambicus derived hydrophobic peptides in protecting the skin against UVA-induced damage

This study explores the bioactive properties of peptide fractions obtained from tilapia fish scale collagen peptide, with a focus on their potential for skincare applications. Peptide fraction F5 demonstrated significant anti-UVA activity by effectively reducing oxidative stress and inhibiting elastase activity. Analysis of amino acid composition revealed a high concentration of specific amino acids in F5, suggesting antioxidant and elastase inhibitory actions. Moreover, compared to conventional antioxidants, F5 exhibited superior efficacy in scavenging free radicals such as ROS. In vitro studies demonstrated F5's ability to promote fibroblast proliferation and migration, contributing to cell repair and tissue regeneration. Mechanistic insights revealed F5's downregulation of MMP-1, MMP-3, and MMP-12 expression, which helps preserve collagen and elastin. Peptide identification and molecular docking analysis provided further understanding of F5's inhibitory mechanism against MMP-12. Overall, these findings indicate the potential of F5 in skincare products and functional foods, offering protection against UVA-induced damage and promoting skin health.

Investigation of the amino acid composition of gluten-free biscuit with carob

The article studies the amino acid composition of the developed biscuit semi-finished products. When developing the recipe for gluten-free products, special attention was paid to the protein composition of the raw materials and the calculation of the amino acid score, since the lack of a certain amino acid affects the ability of gluten formation during the kneading process. In addition, an unbalanced amino acid composition can cause an imbalance in the human body and negatively affect the functioning of muscles, heart, brain and other organs, leading to diseases. The objectives of the research included the following: determination of the amino acid composition of gluten-free biscuit semi-finished products; analysis of amino acid composition and calculation of the amino acid score of gluten-free biscuit products. The amino acid composition was calculated according to well-known methods, taking into account the chemical composition of food products. During the calculation, the biological value of proteins was assessed, the utility coefficient, the amino acid composition balance coefficient, and the amino acid score difference coefficient were determined. It was established that the developed gluten-free biscuit contained a significant amount of threonine, namely 11.38 g per 100 g of protein. As a result of calculations, it was determined that the first limiting amino acid was tryptophan, the second was the compound «phenylalanine + tyrosine», the shares of which in the amino acid score were 0.12 and 0.90, respectively. An assessment of the complex balance of a gluten-free biscuit semi-finished product showed an insufficient level of balance in human nutrition, but the indicators of individual amino acids compared to the control made from wheat flour were higher, for example, valine by 1.8 times, isoleucine, leucine and lysine by 1.1 times, metheonine + cysteine 2.7 times and threonine 2.8 times.

Analysis of Free Amino Acid Composition and Honey Plant Species in Seven Honey Species in China.

Honey is well-known as a food product that is rich in active ingredients and is very popular among consumers. Free amino acids (FAAs) are one of the important nutritional components of honey, which can be used not only as a nutritional indicator of honey but also as an indicator of plant source identification. In this study, the contents of 20 FAAs in seven types of honey from 11 provinces in China were examined for the first time. The 20 FAAs were analyzed by ultra-performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS). By analyzing 93 honey samples from seven types of honey, the FAAs were found to range from 394.4 mg/kg (linden honey) to 1771.7 mg/kg (chaste honey). Proline ranged from 274.55 to 572.48 mg/kg, and methionine was only present in some of the linden honey, chaste honey, acacia honey, and rape honey. Evaluated by amino acid principal component analysis, multifloral grassland honey had the highest overall evaluation score, acacia and jujube honey were the most similar, while chaste honey was the least similar to the other types of honey. In addition, DNA was extracted from 174 Xinjiang grassland honey samples and different plant leaves for PCR and sequencing to identify the species of nectar plants. As a result, 12 families and 25 species of honey plants were identified. The results confirmed the diversity of FAAs in dissimilar types and sources of honey. This study provides a reference for expanding honey quality standards and verifying the authenticity of honey.

Exploring lipid health indices and protein quality in ninety Indian linseed varieties by comprehensive analysis of fatty acid composition, lignan content, and amino acid composition

Biochemical profiling of 90 linseed (Linum usitatissimum L.) varieties was done to have insights into their health benefits and nutritional properties. The analysis of fatty acid (FA) composition revealed 5 major FAs as α-linolenic acid (ALA), linoleic acid (LA), oleic acid (OA), palmitic acid (PA), and stearic acid (SA) ranging from 1.68% to 59.19%, 5.61–62.44%, 18.14–45.54%, 5.69–9.5%, and 3.94–10.29%, respectively. Secoisolariciresinol diglucoside (SDG) content varied significantly with a wide range of 0.02–3.60% in the seed with highest SDG content recorded so far as 3.60% in variety KL-226. Amino acid (AA) composition analysis revealed the variation in average amino acid content of essential amino acids (EAA) (His, Thr Val, Met, Trp, Phe, Ile, Leu, Lys) and non-essential amino acids (NEAA) (Asp, Glu, Ser, Gly, Arg, Ala, Tyr, Cys). Total NEAA content ranged from 3.24% to 23.69% while total EAA content ranged from 1.89% to 14.89%. Lipid heath indices such as atherogenicity index, thrombogenicity index, cholestrolemic index and peroxidisability index along with other fatty acid ratios such as n-6/n-3 ratio, UFA/SFA, PUFA/SFA were calculated to determine the stability of the varieties against auto-oxidation. It also revealed the positive effect of all varieties providing protection against atherosclerosis, coronary heart diseases, cancer and inflammatory diseases. Oleic desaturation ratio (ODR) and linoleic desaturation ratio (LDR) calculated to determine the desaturation efficiency of fatty acids, while protein efficiency ratio (PER) value calculated using amino acid composition determine the nutritional quality of protein. PER value ranged from 1.92 to 4.12 making all 90 varieties a good quality protein plant source. Principal component analysis revealed a significant variation between the fatty acid composition, amino acid composition and SDG content with a total variation of 69.95%. Hierarchical cluster analysis calculated using Pearson correlation coefficient revealed that 89 varieties are mostly similar except TL-99 variety.

Microencapsulation of Lactobacillus plantarum with Improved Survivability Using Pufferfish Skin Gelatin-Based Wall Materials.

To improve the survivability of probiotics, Lactobacillus plantarum was microencapsulated using pufferfish skin gelatin (PSG)-based wall materials by spray-drying. This work investigated the protective effect of three different pH-dependent proteins (sodium caseinate (SC), soy protein isolate (SPI), and whey protein isolate (WPI)) combined with PSG on L. plantarum. The experimental results of spray-drying with an inlet temperature of 120 °C and an outlet temperature of 80 °C, storage at 4 °C for 6 months, simulated digestion, and turbidity indicated that PSG/SC had better stability and encapsulation effects and was more suitable to encapsulate L. plantarum than PSG/SPI and PSG/WPI. The optimum preparation conditions for L. plantarum microcapsules were a PSG/SC mass ratio of 2:1, an SC concentration of 20 g/L, and a cell concentration of 10 g/L. The encapsulation efficiency of the obtained microcapsules was 95.0%, and the survival rate was 94.2% in simulated gastric fluid for 2 h and 98.0% in simulated intestinal fluid for 2 h. Amino acid composition analysis exhibited that the imino acid and aspartic acid contents of PSG were 27.98 and 26.16 g/100 g protein, respectively, which was much higher than commercial bovine gelatin. This characteristic was favorable to the high encapsulation efficiency and stability of microcapsules. In vitro release experiments showed that the PSG/SC microcapsules did not disintegrate in simulated gastric fluid for 2 h but could completely release in simulated intestinal fluid for 2 h, which can maintain the high survivability of L. plantarum in simulated digestion. In general, this study demonstrated that microcapsules using PSG/SC as wall materials can effectively improve the survivability of probiotics and have great potential for application in probiotic products.

Excellent iron-chelating capacity of Yesso scallop (Patinopecten yessoensis) skirt hydrolysate fermented by Bacillus subtilis M17-b7

Peptide ferrous chelate is a new type of biological iron, which has the advantages of high absorption rate, safety and no digestive tract irritation. In this study, microbial fermentation was used for the first time to prepare iron-chelating peptides. Forty-eight strains were applied to ferment scallop skirts. A dominating strain was eliminated by using the iron binding capacity of the scallop skirt hydrolysate as the screening index. The scallop skirt hydrolysate fermented by Bacillus subtilis M17-b7 showed excellent iron-chelating capacity (96.20% ± 0.03%). Meanwhile, the structure, morphology and bioactivity of fermented scallop skirt hydrolysate (FSH) and fermented scallop skirt hydrolysate-iron (FSH–Fe) were measured. Based on the amino acid composition and spectral analysis, it was confirmed that the significant amino acids contains carboxyl, carbonyl, and amino groups. The result of scanning electron microscope indicated that the surface of FSH became porous and the particles were bigger after chelating with ferrous. Moreover, the peptide-ferrous chelate was more stable in salt solutions and simulated gastric juice compared with ferrous sulfate. It is also noteworthy that the preparation of ferrous chelate peptides by fermentation is cost-effective compared with enzymatic hydrolysis. Therefore, this study provides theoretical support for the use of fermentation as a promising tool to produce peptide-ferrous chelate.

Genomic basis of environmental adaptation in the widespread poly-extremophilic Exiguobacterium group.

Delineating cohesive ecological units and determining the genetic basis for their environmental adaptation are among the most important objectives in microbiology. In the last decade, many studies have been devoted to characterizing the genetic diversity in microbial populations to address these issues. However, the impact of extreme environmental conditions, such as temperature and salinity, on microbial ecology and evolution remains unclear so far. In order to better understand the mechanisms of adaptation, we studied the (pan)genome of Exiguobacterium, a poly-extremophile bacterium able to grow in a wide range of environments, from permafrost to hot springs. To have the genome for all known Exiguobacterium type strains, we first sequenced those that were not yet available. Using a reverse-ecology approach, we showed how the integration of phylogenomic information, genomic features, gene and pathway enrichment data, regulatory element analyses, protein amino acid composition, and protein structure analyses of the entire Exiguobacterium pangenome allows to sharply delineate ecological units consisting of mesophilic, psychrophilic, halophilic-mesophilic, and halophilic-thermophilic ecotypes. This in-depth study clarified the genetic basis of the defined ecotypes and identified some key mechanisms driving the environmental adaptation to extreme environments. Our study points the way to organizing the vast microbial diversity into meaningful ecologically units, which, in turn, provides insight into how microbial communities adapt and respond to different environmental conditions in a changing world.

Comprehensive amino acid composition analysis of seed storage proteins of cereals and legumes: identification and understanding of intrinsically disordered and allergenic peptides

The seed storage proteins of cereal and legumes are the primary source of amino acids which are required for sustaining the nitrogen and carbon demands during germination and growth. Humans derive most of their dietary proteins from storage proteins in form of a wide variety of foods, for consumption. The amino acid content of most of these proteins is biased and the need for this biasness is not understood. The high abundance of proline, glutamine, and cysteine in cereals makes the gluten fraction viscoelastic. The cereal proteins have less charge and legume proteins have more charge on them. Their non-polar amino acid distribution has large variations. These characteristics are strongly responsible for the partial and complete unfolding of several domains of the storage proteins. Many of the storage proteins share a highly conserved structural feature within the cupin superfamily spread across all kingdoms of life. The intrinsically disordered viscoelastic proteins help in making dough which is vital for the quality of bread. Unfolded regions harbor more immunogenic sequences and cause food-related allergies and intolerance. We have discussed these properties in terms of comparison of cereal and legume storage protein sequences and allergy. Our study supports the findings that large disordered regions contain allergen-representative peptides. Interestingly, a high number of allergen-representative peptides were cleavable by digestive enzymes. Furthermore, unfolded storage proteins mimic microbial immunogens to induce a memory immune response. Results findings can be used to guide the understanding of immunological characteristics of storage proteins and may assist in treatment decisions for food allergy. Communicated by Ramaswamy H. Sarma

Orange fleshed sweet potato-rice bran flour: Optimization, proximate and amino acid composition for dough meal production

This study focuses on optimizing the proximate composition of dough meal made from blends of orange-fleshed sweet potato, defatted sesame, and rice bran flour. The utilization of these readily available local ingredients demonstrates significant potential for enhancing the nutritional value of staple foods. The research employs a systematic approach to determine the optimal proportions of these three flours, with the goal of achieving a balanced profile of essential nutrients. Parameters such as moisture, protein, fat, carbohydrate, and dietary fiber content were analyzed for the optimized blends. The observed ranges for moisture, ash, protein, fat, fiber, and carbohydrates in the flour samples were 0.99–3.31, 1.44 - 8.88, 6.25 - 13.97, 6.09 - 12.22, 2.22 - 5.00, and 66.22 - 77.21g/100g, respectively. The optimal blends were determined using response surface methodology software, with a focus on achieving high protein and fiber content. Functional, pasting, and amino acid composition analyses were performed on these optimum blends. In conclusion, the optimized flour blends of orange-fleshed sweet potato, defatted sesame, and rice bran present a viable alternative to conventional unripe plantain flour for dough meal production. This research bridges the gap between traditional staples and nutritional enrichment, offering potential solutions for addressing nutritional deficiencies and promoting sustainable dietary practices. The findings contribute to the development of innovative food formulations that cater to both nutritional needs and consumer preferences.

A novel integrated automatic strategy for amino acid composition analysis of seeds from 67 species.

The composition and quantity of amino acids (AAs) in seeds are complicated due to the various origins and modifications of different species. In this study, a novel automatic neutral loss filtering (ANLF) strategy based on accurate mass searching by Python was developed to analyze the free and hydrolyzed AA-phenyl isothiocyanate (PITC) derivatives from seeds of Gymnosperm and Angiosperm phyla. Compared with traditional strategies, ANLF showed much higher accuracy in screening AA derivatives by filtering nitrogen-containing non-AA compounds and efficiency in processing large datasets. Meanwhile, the content phenotype of 20 proteinogenic AAs from seeds of these two families was characterized by a 35-min HPLC method combined with an automated peak-matching strategy. AA profiles of 232 batches of seeds from 67 species, consisting of 19 proteinogenic AAs, 21 modified AAs, and 77 unknown AAs, would be a good reference for their application in food and medicine.

A comparison of nutritional components and memory enhancement effects of HongJam prepared from different silkworm varieties that weave yellow-colored cocoons

Hongjam (HJ) is a natural health food made from mature silkworms, and various health-promoting effects of HJ have been reported. Recent studies have reported that the health-promoting effects of HJ vary depending on the color of the cocoon of the silkworm variety used for its production. Recently, we reported that Golden Silk (GS), a variety of silkworm with yellow cocoons, exhibit superior memory improvement effects when HJ derived from these silkworms is compared to other varieties. However, breeding lines used to produce silkworm varieties are maintained through inbreeding, which can lead to serious side effects in the case of the GS variety. Therefore, it is necessary to investigate the nutritional components and health-promoting effects of Daehwangjam (DHJ), a recently established yellow cocoon silkworm variety.A comparative study was conducted on the nutritional components and memory-enhancing effects of GS and DHJ-HJ. We found no significant differences in nutrient composition between GS- and DHJ-HJ as determined through proximate analysis, amino acid composition analysis, fatty acid content analysis and other methods. Additionally, in a rodent model of mild cognitive impairment, DHJ-HJ proved to be equally effective as GS-HJ. Since DHJ produces larger mature silkworms than GS, it will be possible to efficiently produce HJ for the purpose of creating memory enhancement health food.

Valorization of sturgeon notochord to obtain antioxidant non-collagenous peptides from the purification process of chondroitin sulfate

Notochord is a cartilage-related by-product of sturgeon processing. To increase the utilization of notochord, we have developed an efficient and eco-friendly extraction process that could recycle non-collagenous peptides during chondroitin sulfate (CS) extraction. Alkaline treatment and ultrafiltration were the two critical steps in the overall extraction process. The results of SDS-PAGE and amino acid composition analysis demonstrated that peptides in low molecular fraction were mainly derived from non-collagenous protein. The non-collagenous peptides exhibited high antioxidant activity. The structural analysis (UV, FTIR, 1H NMR and SAX-HPLC) of CS in high molecular fraction proved high purity CS was obtained using new extraction process. The yield of non-collagenous peptides and CS were 16.8% and 14.5%, respectively. Including undenatured type II collagen, the total utilization rate of notochord was increased to 75.6%. It truly realized the maximum utilization of sturgeon notochord. This extraction process can be used as a reference for other cartilage-related by-products.

Comparative analysis of physico-chemical, organoleptic parameters and amino acid composition of various types of poultry meat

The article presents the results of studies of physico-chemical and organoleptic parameters of various types of poultry meat. One of the important indicators in determining the quality of raw materials and when choosing them as raw materials for further processing is its physico-chemical properties and organoleptic indicators. Under laboratory conditions, the results of a study were obtained to determine the physico-chemical parameters (moisture, protein, fat, ash, pH, moisture binding ability of minced meat), organoleptic parameters (appearance, color, smell, consistency, transparency and aroma of broth, juiciness) of the quality of poultry meat of various types. The most commonly consumed types of poultry meat were purchased as research samples: broiler poultry, turkey meat and duck meat. According to the results of the study of physico-chemical studies, it was found that turkey breast fillet contains more protein and less fat than broiler breast fillet and duck. The highest moisture binding capacity was observed in turkey meat 78.3%. The pH results of the studied samples showed the value of fresh meat suitable for further processing for the production of meat products. The article also presents the results of a comparative assessment of the biological value of poultry meat. The results of the study make it possible to assess the quality of regional raw materials.

Protein Quality Characterization of Defatted White Sesame Cake and Its Protein Isolate

Present work evaluated the protein quality of defatted white sesame flour and the protein isolates obtained from sesame cake through the alkaline extraction at a pH 9.5. The study was conducted at Department of Foods and Nutrition, Post Graduate and Research Center (PGRC), College of Community Science and MFPI - Quality Control Laboratory, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad (India) during 2021-2023. Defatted white sesame cake was subjected to alkaline extraction at pH 9.5 and resultant isolates were evaluated for nutrient composition, scanning electron microscope imaging, amino acid composition and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The obtained data was subjected to one-way analysis of variance. The white sesame protein isolates had a protein content of 93.83%, isolate recovery of 37.00 g/100 g and protein yield of 71.77%. The non-essential amino acids (NEAAs) content of the defatted white sesame flour and white sesame protein isolates ranged between 68.06% to 70.60% of the total protein content, while 29.40% to 31.94% was essential amino acids (EAAs). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of defatted white sesame flour WSF and white sesame protein isolate (WSPI) exhibited protein bands within the molecular weight range of 20 to 62 kDa. The protein isolates derived from sesame seed cake has promising potential for integration into diverse food formulations, offering an avenue to combat protein deficiencies.

STRUCTURAL PREDICTION OF HUMAN ZIP 2 AND ZIP4 BASED ON HOMOLOGY MODELLING AND MOLECULAR SIMULATION

Objective: This study aimed to analyze the structural proteins of zinc transporters as the target for drug actions and their molecular interactions. Methods: The present study is about the homology modelling and analysis of the zinc transporter function using the in silico molecular modelling method. Homology modelling predicts the 3D structure of a protein based on the sequence alignment with one or more template proteins of known structure. This study using in silico molecular modelling method, explains the 3D structure of human ZIP 2 and ZIP4 with Ramachandran Plot analysis, physical and chemical characteristics, transmembrane prediction with structural biology, and binding site prediction through molecular docking simulation. Results: Based on the physicochemical properties of the 3D structure of the ZIP2 and ZIP4 proteins, each comprises 309 amino acids and 582 amino acids with pI values of 5.85 and 5.24. The amino acid composition analysis showed that both proteins contain many Leucine amino acids. The Ramachandran diagram concludes that both proteins are stable in the stereochemical conformation forming a secondary structure. The binding amino acids on ZIP2 include Glu281, His216, Ser284, and Arg46. The binding amino acids in ZIP4 include Gln148, Gln154, Thr155, His197, Ala138, and Lys157. Conclusion: Establishment of the structure and function of human ZIP2 and ZIP4 as zinc transporters in cell membranes and prediction of ZIP2 and ZIP4 binding sites through molecular dcoking.

Deepening in the understanding of the role of collagen subunits on the differential molecular arrangement of P. glauca and M. merluccius marine collagens

Decades of extensive efforts on marine collagen extraction and characterization allowed to recognize the unique and excellent characteristics of marine collagen offering advantages over that obtained from terrestrial sources. However, not all marine collagens have the same biochemical characteristics; understanding those at molecular and supramolecular level, is crucial for optimal design of applications. One relevant aspect of collagen characterization is the analysis of its different subunits (α-chains) and their intermolecular cross-links (β- and γ-components), which ultimately determine the specific functions of a particular collagen. Collagens from a teleost and an elasmobranch species were analyzed to understand the influence of their subunit composition and intermolecular crosslinking pattern on their different physicochemical behaviour. For comparative purposes a commercial mammal collagen was included in the study. Although electrophoretic profiles showed the typical composition of type I collagen for hake, blue shark and calf collagen, molar ratios of their α-chains were different indicating a different degree of dimerization of their α2-chains with implications in the presence of a different crosslinking degree pattern. Electrophoresis, amino acid composition, hydrophobicity (RP-HPLC) and molecular weight analysis (GPC-HPLC) results, besides a peptide mapping and an antioxidant activity study of the resultant peptides, would help to understand the role of different subunit collagen composition and different crosslinking pattern in the conformation of a differential quaternary supramolecular structure within different species and its biofunctional implications. The experiments developed would allow to progress in the valorization potential of fish discards and byproducts to explore commercial uses of collagens from marine origin.

A novel salt- and organic solvent-tolerant phosphite dehydrogenase from Cyanothece sp. ATCC 51142.

Phosphite dehydrogenase (PtxD) is a promising enzyme for NAD(P)H regeneration. To expand the usability of PtxD, we cloned, expressed, and analyzed PtxD from the marine cyanobacterium Cyanothece sp. ATCC 51142 (Ct-PtxD). Ct-PtxD exhibited maximum activity at pH 9.0°C and 50°C and high stability over a wide pH range of 6.0-10.0. Compared to previously reported PtxDs, Ct-PtxD showed increased resistance to salt ions such as Na+, K+, and NH4 +. It also exhibited high tolerance to organic solvents such as ethanol, dimethylformamide, and methanol when bound to its preferred cofactor, NAD+. Remarkably, these organic solvents enhanced the Ct-PtxD activity while inhibiting the PtxD activity of Ralstonia sp. 4506 (Rs-PtxD) at concentrations ranging from 10% to 30%. Molecular electrostatic potential analysis showed that the NAD+-binding site of Ct-PtxD was rich in positively charged residues, which may attract the negatively charged pyrophosphate group of NAD+ under high-salt conditions. Amino acid composition analysis revealed that Ct-PtxD contained fewer hydrophobic amino acids than other PtxD enzymes, which reduced the hydrophobicity and increased the hydration of protein surface under low water activity. We also demonstrated that the NADH regeneration system using Ct-PtxD is useful for the coupled chiral conversion of trimethylpyruvic acid into L-tert-leucine using leucine dehydrogenase under high ammonium conditions, which is less supported by the Rs-PtxD enzyme. These results imply that Ct-PtxD might be a potential candidate for NAD(P)H regeneration in industrial applications under the reaction conditions containing salt and organic solvent.

Comparative Analysis of Amino Acid and Biogenic Amine Compositions of Fermented Grape Beverages.

Amino acids and biogenic amines are important components of food and beverages. In grape-derived products such as wine and wine vinegar, they can have different origins and can influence the odor and taste of the products. Their concentration is influenced by the grape variety, vintage, and winemaking process. In our study, we carried out an LC-MS-based comparative analysis of 22 grape-derived beverages, including three different wine types and four wine vinegar samples from the Tokaj region in Hungary. The concentrations of 23 amino acids and 10 biogenic amines were examined, and the differences among the sample types were analyzed. The differences in the concentrations of some metabolites between Aszú-Furmint pairs originating from the same wineries and year provide information on the effect of botrytized grape on wine composition. Our data can provide further evidence on how the production process shapes the metabolite content of beverages and highlight the nutritional value of wine vinegar.