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423 results on '"Zhang, Lujia"'

132. Structure-based substrate screening for an enzyme

Author

Wei Dongzhi, Wang Xuedong, Zhang Lujia, Xu Tao, and Li Tianbi

Subjects
Computer applications to medicine. Medical informatics, R858-859.7, Biology (General), QH301-705.5
Abstract

Abstract Background Nowadays, more and more novel enzymes can be easily found in the whole enzyme pool with the rapid development of genetic operation. However, experimental work for substrate screening of a new enzyme is laborious, time consuming and costly. On the other hand, many computational methods have been widely used in lead screening of drug design. Seeing that the ligand-target protein system in drug design and the substrate-enzyme system in enzyme applications share the similar molecular recognition mechanism, we aim to fulfill the goal of substrate screening by in silico means in the present study. Results A computer-aided substrate screening (CASS) system which was based on the enzyme structure was designed and employed successfully to help screen substrates of Candida antarctica lipase B (CALB). In this system, restricted molecular docking which was derived from the mechanism of the enzyme was applied to predict the energetically favorable poses of substrate-enzyme complexes. Thereafter, substrate conformation, distance between the oxygen atom of the alcohol part of the ester (in some compounds, this oxygen atom was replaced by nitrogen atom of the amine part of acid amine or sulfur atom of the thioester) and the hydrogen atom of imidazole of His224, distance between the carbon atom of the carbonyl group of the compound and the oxygen atom of hydroxyl group of Ser105 were used sequentially as the criteria to screen the binding poses. 223 out of 233 compounds were identified correctly for the enzyme by this screening system. Such high accuracy guaranteed the feasibility and reliability of the CASS system. Conclusion The idea of computer-aided substrate screening is a creative combination of computational skills and enzymology. Although the case studied in this paper is tentative, high accuracy of the CASS system sheds light on the field of computer-aided substrate screening.

Published
2009
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133. Identification of three new compounds that directly target human serine hydroxymethyltransferase 2.

Author

Han, Yanfang, He, Liping, Qi, Yifei, Zhao, Yue, Pan, Yue, Fang, Bohuan, Li, Sha, Zhang, John Z. H., and Zhang, Lujia

Subjects
THYMIDYLATE synthase, TETRAHYDROFOLATE dehydrogenase, SERINE, PROTEIN expression, TARGETED drug delivery
Abstract

Mitochondrial serine hydroxymethyltransferase 2 (SHMT2) is an important drug target in the one‐carbon metabolic pathway, since its activity is critical for purine and pyrimidine biosynthesis. Additionally, it plays a prominent role during metabolic reprogramming of cancer cells, and SHMT2 inhibitors have proven useful as anticancer drugs. Compared to drugs targeting one‐carbon metabolic enzymes (mainly dihydrofolate reductase and thymidylate synthase) that have been used for clinical treatment of cancer, efficient SHMT2‐specific inhibitors are lacking. Therefore, we established a direct system for virtual screening, protein expression, and identification of inhibitors targeting SHMT2. First, 27 compounds qualifying as potential SHMT2 inhibitors were selected for biological activity verification through virtual screening of the 210 thousand compounds registered in the Specs database. Second, these 27 hits were subjected to quick screening by an in vitro non‐competitive kinetic assay of SHMT2 single‐enzyme catalysis. This allowed us to identify three compounds featuring medium‐strength and non‐competitive inhibition of SHMT2: AM‐807/42004511 (IC50 = 14.52 ± 4.1665 μM), AM‐807/40675298 (IC50 = 12.74 ± 5.8991 μM), and AM‐807/42004633 (IC50 = 9.43 ± 0.5646 μM). We describe a quick screening method for the identification of inhibitors targeting SHMT2, providing a basis for subsequent identification and screening of new inhibitors. [ABSTRACT FROM AUTHOR]

Published
2021
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134. Isolation and application of aflatoxin-oxidase based on magnetic protein label.

Author

MA Meng, GAO Bei, LIU Yao, FANG Bohuan, JIANG Min, ZHU Tong, ZHANG Zenghui, and ZHANG Lujia

Abstract

The separation of aflatoxin-oxidase ( AF0) based on pigeon magnetic protein ( clMagR) label' and the aflatoxin B1( AFB1) scavenging system were established.The gene AFO was co-encoded with the clMagR gene'then inserted into pET-28a(+) and transformed into E. coli BL21(DE3) for heterologously expression of fusion protein. After optimization of the expression conditions' we explored rapid separation and purification of AFO based on the physical adsorption of magnetic nanoparticles and magnetic proteins. In addition, the purified AFO was applied to the detoxification assay of AFBl.The magnetic protein label could slightly increase the soluble protein expression of AFO.At the same time,the magnetic protein-labeled AFO had good magnetic induction and was efficiently separated by adsorption with magnetic nanoparticles. The detoxification rate of AFB1 was 75. 94% using purified AFO,which could be reused for 13 times.We developed a novel strategy for the separation of aflatoxin-oxidase,and applied into biological detoxification of aflatoxin. This strategy provides promising utilization for further protein separation research and applications. [ABSTRACT FROM AUTHOR]

Published
2021
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147. Cloning, purification and biochemical characterization of recombinant Cathepsin L from Takifugu rubripesand its role in taste formation

Author

Tang, Qilong, Wang, Wenli, Zhang, Lujia, and Liu, Yuan

Abstract

In recent years Takifugu rubripeshas been increasingly popular among people base on its good taste. Cathepsin L was related to the formation of amino acids and small peptides. This study described the biochemical characterization of Cathepsin L and its role in the taste formation of Takifugu rubripes. Cathepsin L gene from Takifugu rubripestissues was cloned successfully, and Cathepsin L with molecular masses of 46 kDa was isolated and enzymatically characterized. This enzyme reached its highest activity at 40 °C and pH 5.5. Cu2+and Mn2+ions reduced the activity of Cathepsin L, but Fe3+and Ca2+ions prominently increased its activity when the final concentrations of metal ions were 1 mM and 5 mM, respectively. The addition of phenylmethanesulfonyl fluoride gradually decreased the enzyme activity over 0.5 mM. 200–3000 KDa fraction from Takifugu rubripesmuscle after Cathepsin L hydrolysis showed the stronger kokumi and umami taste, especially kokumi. In this study, the recombinant Cathepsin L from Takifugu rubripescould play a role in flavor formation and be applied in flavor studies through the degradation of animal proteins.

Published
2020
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