Professor Zhang Guowen team of Nanchang University: Comparing the inhibition effect of no-eating catetin with no-food caterate and no-eating child's catetin without dinate on tyrosine enzymes

Original title: Professor Zhang Guowen Team, School of Food, Nanchang University: Comparison table no children's tea without dinate and no food children's catetin without caterate inhibition of tyrosinease and its combined inhibition effect with quic acid
chin-3-gallate and gallocatechin gallate againststt tyrosinase and their combined effects with kojic acid, which systematically studies the binding properties of table-free cerium without cerpene and no-food cerium without cerium with tyrosinease, the inhibition mechanism of TY and its combined inhibition effect with quic acid, The results of the study are of great theoretical significance and practical value for the prevention and treatment of pigmentation skin diseases and the control of enzymatic browning of fruits and vegetables. This article will be published online July 1, 2021 by Food Chemistry. Professor Zhang Guowen is the author of this paper.
highlights
table no-eater cerium no-food tyrosine (epigallocatechin-3-gallate, EGCG) and no-food baby tea no-food tyrosine (gallocatechin gallate, GCG) in a hybrid way reversible inhibition of tyrosinease; The combination of
x EGCG and GCG has a synergistic inhibitory effect on tyrosine enzymes;
x hydrophobic action and hydrogen bonds dominate the binding process;
x EGCG and GCG are combined into the active center of tyrosine enzyme; and the binding of
x EGCG and GCG induces the structureal stretching of tyrosinease.
Theintroduction
tyrosinase (tyrosinase, TY) is a key enzyme in melanin production and play an important role in controlling food browning and pigmentation skin diseases. When TY is overexposed or overactive, melanin may overexploit and aggregate, leading to skin diseases, food browning, shrimp blackness, etc. Inhibiting TY's catalytic activity, preventing tyrosine oxidation to melanin and reducing melanin production have become the main ways to prevent melanin-addicted skin diseases and control food enzymatic browning. Tea is one of the world's three famous beverages, in foreign countries enjoy the "healthy liquid, soul drink" of the name, in our country is known as "national drink", tea is beneficial to health. Theotin is a kind of polyphenol compound, is the main component of tea polyphenols, accounting for about 65% to 80% of the total amount of tea polyphenols, but also tea has one of the main components of health function. In recent years, some studies have shown that the uterine table has no eater of cerium without EGCG and no eater of cerium without cerium without glycerides (GCG) has good in-body inhibition activity on TY, but the molecular mechanism of co-inhibition of TY is not clear, limiting the application of cedean as a natural TY inhibitor research. Professor Zhang Guowen's team at Nanchang University School of Food systematically studied the binding properties of EGCG and GCG and TY, the inhibition mechanism of TY and its combined inhibition effect with curric acid, and the results of the study have important theoretical significance and practical value for the prevention and treatment of pigmentation skin diseases and the control of enzymatic browning of fruits and vegetables, and provide experimental basis for the dietary nutrition of catetin.
Results and Discussion
Inhibition of TY by EGCG and GCG
EGCG and GCG were both concentration-dependent inhibition of TY activity, with half of the inhibited concentrations IC50 values of 39.4 ± 0.54 m and 36.8 ± 0.21 m (Figure 1), respectively. EGCG and GCG are typical polyphenol compounds with multiple hydroxyls, and these structures are very beneficial for producing hydrogen bonds with TY amino acid residues, thus promoting the binding of catetin with TY and reducing TY's catalytic capacity. Both EGCG and GCG inhibit TY activity in a mixed manner, and they inhibit the activity of enzymes by competing with the substrate to bind to the active center of TY. GCG contains a cerpenol-based group in the trans-composition, which may lead to increased tolerance and flexibility in interaction with large molecules or solvents, thus contributing to its inhibition of TY.
EGCG, GCG and curric acid on TY joint inhibition
compared with EGCG, GCG alone inhibition of TY activity, the ability of EGCG and curric acid to inhibit the use of inhibition as TY decreased, while GCG and curric acid, EGCG and GGC combined inhibition of TY (Figure 2). It is inferred that the inhibition of TY by EGCG and curric acid is an antagonistic, that GCG and curric acid are inhibited by TY, and that EGCG and GCG in association can inhibit TY in concert.
EgCG, GCG and TY binding characteristics
the results show that EGCG, GCG can form a base complex with TY and statically annihilate TY endofluence, at the same temperature, GCG shows a stronger fluorescent annihilation capacity (Figure 3). EGCG and GCG have 1 binding bit on TY, but the binding constant value of GCG and TY is higher than EGCG, indicating that GCG is more likely to bind to TY, which is due to the difference between the smooth and trans-composition of the cerpol group, resulting in the space bit resistance of GCG is less than EGCG. The results of the thermodynamic analysis show that hydrophobic forces and hydrogen bonds play an important role in the formation and stability of EGCG/GCG-TY complexes.
EGCG and GCG's effect on TY's composition
The synchronous fluorescence spectrum showed that neither EGCG and GCG significantly affected the hydrophobic and polarity of Tyr and Trp residues, that the binding points of EGCG and TY were closer to Tyr residues, and that the binding points of GCG and TY were closer to Trp residues. The two chromatography results show that with the addition of EGCG or GCG, the secondary structure content of TY changes significantly (Figure 4), when the molar ratio of EGCG to TY increases from 0:1 to 8:1, The molar ratio of GCG to TY increased from 0:1 to 1:1, and EGCG and GCG reduced TY's α-helix content from (32.16 ±0.65 per cent) to (29.69 ±0.63 per cent) and from (27.62 ± (0.20) % to (23.44 ± 0.96), resulting in an increase in b-folding content from (21.73 ±0.22) to (24.92 ± (0.13 per cent) and increase from (24.74 ± 0.81 per cent to (29.84 ± 0.32 per cent), EGCG or GCG in combination with TY results in partial extension of the enzyme structure. GCG induces a more pronounced change in TY structure than EGCG, which may explain why GCG has stronger TY inhibition than EGCG.
molecular docking study
the results showed that EGCG was associated with the amino acid residue His244 by hydrophobic force. Val248, His263, Ser282 and Val283 interact, polar solventation freedom can account for a large proportion of total free energy, EGCG in the A ring C5-OH (H) and D ring C11'-OH (H) and TY In His85 (O) and Met280 (O) respectively form two hydrogen bonds. The GCG is surrounded by His61, His85, Gly86, His244, Val248, His259, His263, Arg268, Val283 and Glu322 residues and four hydrogen bonds are observed (Figure 5). In addition, His244, Val248 and Val283 participate in the formation of hydrophobic interactions, based on molecular forces/Poisson-Boltzmann surface area (MM-PBSA) free energy decomposition analysis, the results show that polar solventation free energy can contribute the most to total free energy. Hydrogen bond and hydrophobic interaction play an important role in stabilizing the structure of the EGCG/GCG-TY complex, which is consistent with the results of fluorescence titration experiments. Importantly, both EGCG and GCG interact with copper ions, while His61, His85, His244, His259 and His263 are located at the active center of TY, further evidence that EGCG and GCG may occupy the location of the active central substrate, changing the structure of TY by reversing the structure of the polypeptide chain, thereby destroying the enzyme activity point to prevent the substrate from being catalyzed by TY and ultimately inhibiting the catalytic activity of the enzyme.
molecular dynamics simulation
further evaluated the structure and properties of the EGCG/CG-TY complex. Figure 6 shows that when combined with EGCG or GCG, the volatility of the EGCG/GCG-TY complex is reduced and the stability of the enzyme is enhanced. The combination of EGCG and TY makes the TY structure loose, but no similar effects have been observed in GCG-TY binding. The difference between TY and EGCG/GCG-TY compounds is not obvious, but the amino acid residues including 60-90, 240-260 and 280-290 show significant fluctuations, proving that the high amino acid residue flexibility is the main cause of the rise and fall values of high-equidox roots, but the interaction between enzymes and inhibitors also affects the average square root rise and fall values. The presence of EGCG and GCG had no significant effect on solvent accessability surface area in TY. Molecular dynamics simulation results support the above experimental results. Due to the changing relative position between EGCG or GCG and TY, the number of hydrogen bonds between EGCG and TY increases and changes between 0 and 7. From the beginning, hydrogen bonds are produced between GCG and TY, and the number of hydrogen bonds gradually increases and changes between 0 and 6. These results further confirm the results of molecular docking, indicating that hydrogen bonds play an important role in the interaction between EGCG or GCG and TY.
Conclusions
Both EGCG and GCG showed synergetic inhibition effect on TY with better TY inhibition activity, which was mixed type, and EGCG and GCG combined use showed synergetic inhibition effect on TY. Hydrophobic forces and hydrogen bonds promote the spontaneous binding of EGCG and GCG to TY, and lead to static annihilation of TY endogene fluorescence. The presence of EGCG and GCG had no significant effect on the micro-environment of Tyr and Trp residues in TY, but induced a decrease in the α-helix content and an increase in the b-folding content, which led to the extension of the TY structure. Molecular docking results show that EGCG and GCG interact with amino acid residues in TY active cavities by hydrophobic and hydrogen bonds. The analysis of amino acid free energy decomposition proves that hydrophobic forces play a major role in the combination of EGCG or GCG and TY. Molecular dynamics simulations show that hydrogen bonds act as stable composites. EGCG reduces the tightness of the TY structure and makes the TY structure loose. Therefore, it is speculated that EGCG and GCG combine into the active center of TY and interact with copper ions and key amino acid residues, occupy the position of the substrate and cause changes in the secondary structure of TY, thus preventing the substrate from being catalytic, and ultimately reducing the activity of TY. This study provides a theoretical basis for insight into the prevention and treatment of pigmentation skin diseases and food anti-browning mechanisms.
Author's Profile
Professor Zhang Guowen
Zhang Guowen, Ph.D., Second Class Professor, Ph.D. Tutor, currently Vice Dean of the School of Food, Nanchang University. Selected in the 2020 core safety ball "highly cited scientists" list, Jiangxi Province, "100 million talent engineering" candidates, Jiangxi Province, young and middle-aged discipline leaders, Nanchang University Food Science and Technology National Key Laboratory fixed members and academic leaders, the National Natural Science Foundation of China peer review experts, China Engineering Education Certification core experts Member of the Food Safety Expert Committee of Jiangxi Food Safety Committee, Director of Jiangxi Food Science and Technology Association, Director of Jiangxi Province Micro element and Health Research Association, Food Chemistry, Journal of Agricultural and Food Chemistry, Food Hydrocolloids, Food and Function, Food Research International, Food and Chemical Toxicology, LWT - Food Science and Technology, Journal of Functional Foods, Analytical Chemistry, Journal of Hazardous Materials, International Journal of Biological Macromolecules and more than 30 international academic journal reviewers. In recent years, presided over the National Natural Science Foundation, the Ministry of Education Ph.D. Point Fund, the National Key Laboratory Fund, Jiangxi Province, major scientific and technological projects and other national and provincial scientific research projects more than 20, at home and abroad in high-level academic journals published more than 270 papers, of which SCI included more than 120 papers, H index 36, Web of Science included papers were cited more than 3,900 times. Won the second prize of national teaching results 3, Jiangxi Province teaching results first prize 2, second prize 3, the Ministry of Science and Technology "Zhenhua -Wang Zhiyi Science and Technology Poverty Reduction Award", Jiangxi Province, the third prize of natural science 2, the editor-in-chief of 4 teaching materials.
Song Xin Master's
, female, Nanchang University School of Food 2018 master's degree, research direction for functional food and nutrition. 3 papers published in academic journals at home and abroad, including 2 SCI papers, including the cover paper "Addory mechanism of epicatechin gallate in tyrosinase: resed interaction, conformation change and computational simulation" and the paper "Comparing the reseds of the ability of people to epigal" published in Food Chemistry