• Korean Journal of Food Science and Technology
• /
• v.18 no.5
• /
• pp.376-381
• /
• 1986

A hypothesis that Korean home-made fermented soybean products are brown-pigmented in large part by contaminated bacteria is proposed. Twenty six strains of bacteria forming brown pigments in the presence of L-tyrosine were isolated from home-made soybean paste. They were characterized and all were identified as strains of Bacillus subtilis. The isolates produced dark brown to brownish black pigmentation on yeast extract-peptone-glucose agar (YPGA) supplemented with 0.1% L-tyrosine in 72 hours but not on YPGA. They also caused different depress of lighter pigmentation on potato dextrose agar and nutrient agar. When an arbitrarily chosen pigmenting isolate was cultivated in a liquid medium supplemented with L-tyrosine, it began to produce pigments only after cell growth stopped. The tyrosinase enzyme was extracted and the enzyme activity was measured by using L-tyrosine and 3-hydroxytyrosine (L-dopa) as substrates. The crude enzyme preparation porduced pigments at rates of $2.1\;{\times}\;10^{-3}\;and\;5.0\;{\times}\;10^{-3}$ optical density units/min measured at 490㎚ for tyrosine and dopa, respectively. Possible content of L-tyrosine in a soybean paste formula was calculated.

• Korean Journal of Food Science and Technology
• /
• v.19 no.5
• /
• pp.446-450
• /
• 1987

To re-evaluate the browning reactions of fermented soybean products, soy sauce mash with added glucose and/or tyrosine was fermented for 152 days in the presence or absence of oxygen. Glucose negatively affected brown pigmentation either singly or with tyrosine. Tyrosine-added soy sauce mash initially browned at the same rate as the control mash until 127th day and then the former continued to brown at the same steady rate while the control mash stopped further browning. Aerobically incubated mash browned much more than anaerobically incubated one when the browning was compared on the 152nd day of fermentation. More than half of the mash browning was found to be due to the oxygen-related browning during the limited 152 days of fermentation time. Both oxygen-related and oxygen-unrelated browning reactions were found to contribute to the browning of soy sauce mash. Oxygen-related browning, however, was found to be more important than the Maillard browning reaction.

• Journal of Life Science
• /
• v.18 no.8
• /
• pp.1036-1041
• /
• 2008

Methenyltetrahydrofolate synthetase extract was obtained from mouse liver and purified via $30{\sim}70%$ ammonium sulfate fractionation, Fast Q anion exchange and phenyl agarose chromatography. HPLC gel chromatography and SDS-polyacrylamide electrophoresis experiments showed that the enzyme is a monomer with molecular weight of 23 kDa. Optimum temperature and pH were $35^{\circ}C$ and 6.5, respectively. The enzyme was chemically modified only by tetranitromethane and 1-ethyl-3- (3-dimethyl aminopropyl)-carbodiimide (EDC), indicating that tyrosine and carboxylate are in the active site. pH studies showed that 2 tyrosines are involved in the binding of the substrates and a carboxylate in catalysis. Therefore, the chemical mechanism of the enzyme is likely that 2 tyrosines bind to ATP and 5-formylTHFand a carboxylate acts as a general base.

• Microbiology and Biotechnology Letters
• /
• v.34 no.1
• /
• pp.58-62
• /
• 2006

Rapid assay of enzyme is a primary requirement for successful application of directed evolution technology. Halo generation on a turbid plate would be a method of choice for high throughput screening of enzymes in this context. Here we report a new approach to prepare turbid plates, by controlling the crystallization of tyrosine to form needle-like particles. In the presence of tyrosine phenol-lyase (TPL), the needle-like tyrosine crystals were converted to soluble phenol rapidly than the usual rectangular tyrosine crystals. When an error-prone PCR library of Citrobacter freundii TPL was spread on the turbid plate, approximately 10% of the colonies displayed recognizable halos after 24 hours of incubation at $37^{\circ}C$. Representative positives from the turbid plates were transferred to LB-medium in 96-wellplates, cultivated overnight, and assayed for the enzyme activity with L-tyrosine as the substrate. The assay results were approximated to be proportional to the halo size on turbid plates, suggesting the screening system is directly applicable to the directed evolution of TPL. Actually, two best mutants on the turbid plates were identified to be $2{\sim}2.5$ and 1.5-fold improved in the activity.

• Journal of the Korean Chemical Society
• /
• v.36 no.4
• /
• pp.613-615
• /
• 1992

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.211-226
• /
• 2019

Pig CD45, the leukocyte common antigen, is encoded by the PTPRC gene and CD45 is a T cell-type specific tyrosine phosphatase with alternative splicing of its exons. The CD45 is a coordinated regulator of T cell antigen receptor (TCR) signal transduction achieved by dephosphorylating the phosphotyrosine of its substances, including $CD3{\zeta}$ chain of TCR, Lck, Fyn, and Zap-70 kinase. A dysregulation of CD45 is associated with a multitude of immune disease and has been a target for immuno-drug discovery. To characterize its key structural features with the effects of regulating TCR signaling, this study predicted the unknown structure of pig CD45RO (the smallest isoform) and the complex structure bound to the ITAM (REEpYDV) of $CD3{\zeta}$ chain via homology modeling and docking the peptide, based on the known human CD45 structures. These features were integrated into the structural plasticity of extracellular domains and functional KNRY and PTP signature motifs (the role of a narrow entrance into ITAM binding site) of the tyrosine phosphatase domains in a cytoplasmic region from pig CD45RO. This contributes to the selective recognition of phosphotyrosine from its substrates by adjusting the structural stability and binding affinity of the complex. The characterized features of pigCD45RO can be applied in virtual screening of the T-cell specific immunomodulator.

• Korean Journal of Food Science and Technology
• /
• v.27 no.3
• /
• pp.286-289
• /
• 1995

To find composition of white crystals in canned bamboo shoots, the solubility in distilled water or dilute HCl solution, organic acid composition, mineral composition and amino acid composition of white crystals were analyzed. The contents of ash, protein, fat and carbohydrate were 55.12%, 14.21%, 0.70% and 29.97% respectively. Only oxalic acid was detected by HPLC analysis as an organic acid. Judging from solubility of white crystals, the type of salt was Ca-oxalate. The content of calcium was 72.68% in total amount of minerals. The content of tyrosine was 75.23% in total amount of protein. In conclusion, white crystals was constituted by Ca-oxalate and tyrosine complex.

• Journal of Life Science
• /
• v.21 no.1
• /
• pp.31-35
• /
• 2011

Dual-specificity protein phosphatases (DUSPs) constitute a family of protein phosphatase characterized by the ability to dephosphorylate phospho-tyrosyl and phospho-seryl/threonyl residues. Most DUSPs are involved in regulation of cell survival and differentiation. In this study, a human dual-specificity protein phosphatase, DUSP28, was isolated from a human kidney cDNA. The recombinant protein was successfully produed in E.coli and showed sufficient phosphatase activity toward DiFMUP (6,8-difluoro-4-methylumbelliferyl phosphate). Various phosphatase inhibitors and divalent metals were tested for their effects on the DUSP28 phosphatase activity. As a result, $Zn^{2+}$ was found to strongly inhibit DUSP28 phosphatase activity, suggesting DUSP28 is involved in Zn-related signal transduction pathway. Furthermore, the DUSP28 protein preferred phospho-tyrosyl residues to phospho-threonyl residues, implying its physiological roles in the cellular process.

• Journal of the Korean Chemical Society
• /
• v.46 no.3
• /
• pp.296-300
• /
• 2002

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.11
• /
• pp.5350-5355
• /
• 2012

Human tyrosinase (hTyr) catalyzes the first and rate limiting step in the biosynthesis of a skin color determinant, melanin. Although a number of cosmetic companies have tried to develop hTyr inhibitors for several decades, absence of 3D structure of hTyr make it impossible to design or screen inhibitors by structure-based approach. Therefore, we built a 3D structure by comparative modeling technique based on the crystal structure of tyrosinase from Bacillus megaterium to provide structural information and to search new hit compounds from database. Our model revealed that two copper atoms of active site located deep inside and were coordinated with six strictly conserved histidine residues coming from four-helix-bundle. Substrate binding site had narrow funnel like shape and its entrance was wide and exposed to solvent. In addition, hTyr-tyrosine and hTyr-kojic acid, a well-known inhibitor, complexes were modeled with the guide of solvent accessible surface generated by in-house software. Our model demonstrated that only phenol group or its analogs could fill the binding site near the nuclear copper center, because inside of binding site had narrow shape relatively. In conclusion, the results of this study may provide helpful information for designing and screening new anti-melanogenic agents.