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Huang F.,Foshan Science and Technology College | Huang F.,Jinan University | Shan X.-F.,Jinan University | Zhang S.-M.,Jinan University | And 3 more authors.
Modern Food Science and Technology

Selenium (Se) content and distribution of Se-containing biotransformation proteins (SeP) in Se-enriched Streptomyces platensis (SeSP) were explored. Additionally, the in vitro scavenging activity of oxygen free radicals by SeP was studied. Total proteins (TP) in S. platensis were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Se content in different molecular-weight proteins was measured using inductively-coupled plasma mass spectrometry (ICP-MS). Laser ablation (LA)-ICP-MS was used for in situ detection of Se content in purified Se phycocyanin (SePC) within the electrophoresis gel. The in vitro clearance of superoxide and hydroxyl free radicals by SeP was investigated by chemiluminescence. The results showed that Se content in SeSP-TP was 32-fold higher than that in non-enriched S. platensis (SP), reaching 805.48 μg/g, while 75.81% oftotal Se was distributed in low-molecular weight SePs (LMWSeP), with molecular weights ≤ 25 ku. LA-ICP-MS results confirmed that purified SePC subunits contained stable, covalently-bound, active Se. The maximum clearance rate of free radicals by LMWSeP was over 70%. The findings suggest that SeSP cultures could be used to produce active SeP by biotransformation. The LMWSeP components in SeSPs are a source of natural Se with high anti-oxidation activity. Further studies are required to determine the form of Se, transformation mechanism, and in vivo bioactivity. ©, 2015, South China University of Technology. All right reserved. Source

Zhang J.-P.,Xiamen University | Zhang J.-P.,Foshan Science and Technology College | Hu Y.-H.,Xiamen University | Wang Q.,Xiamen University | And 4 more authors.
Journal of Agricultural and Food Chemistry

Heavy metal pollution such as chromium and zinc in the seawater has been increasing in recent years in the China Sea. Marine shellfish such as prawn and crab are sensitive to this pollution. β-N-Acetyl-d-glucosaminidase (NAGase, EC catalyzes the cleavage the oligomers of N-acetylglucosamine (NAG) into the monomer. In this study, taking p-nitrophenyl-N-acetyl-β-d- glucosaminide (pNP-NAG) as substrate, the effects of Zn2+ on NAGase from green crab (Scylla serrata) have been studied. The results showed that appropriate concentrations of zinc could lead to reversible inhibition on the enzyme, and the IC50 has been estimated to be 0.5 ± 0.012 mM. Furthermore, it has been shown that Zn2+ could reduce the thermal stability of NAGase depending on the concentration of Zn2+. The inhibitory kinetics of zinc on the enzyme in the appropriate concentrations has been studied using the kinetic method of substrate reaction. The inhibition model has been set up, and the rate constants have been determined. The results showed that Zn2+ was a mixed-type inhibitor of NAGase and that it could combine at the free enzyme and the enzyme-substrate active sites. © 2010 American Chemical Society. Source

Zhang J.-P.,Xiamen University | Zhang J.-P.,Foshan Science and Technology College | Leng B.,Xiamen University | Leng B.,Zhangzhou Normal University | And 5 more authors.
Protein and Peptide Letters

β-N-acetyl-D-glucosaminidase (NAGase) is a major member in chitinolytic enzymes system, which plays an important role in the hatching and molting processes of marine organism. The effects of guanidinium chloride (GuHCl) on the activity of NAGase from green crab (Scylla serrata) were investigated in this study. In results, GuHCl causes reversible inactivation of the enzyme at below 0.8 M concentrations, and the IC50 is estimated to be 0.15 M. The relationship between the enzyme activity and conformation was charaterized by monitoring the change of protein fluorescence spectra. With increasing GuHCl concentration, the fluorescence intensity of the enzyme distinctly decreases, and the maximal emission peaks appear red-shifted (from 338 nm to 343 nm). The enzyme inactivation precedes conformational changes, indicating that the enzyme active site is more flexible than the whole enzyme molecule. The result of the kinetics of inactivation shows that the value of k+0 is larger than that of k+0'. It suggests that the substrate could protect the enzyme to a certain extent during guanidine denaturation. Our results provide important new insights in marine organism culture, especially in crustacean growth. © 2012 Bentham Science Publishers. Source

Zhuang Q.J.,South China Agricultural University | Zhang H.J.,Foshan Science and Technology College | Lin R.Q.,South China Agricultural University | Yuan Z.G.,South China Agricultural University | And 4 more authors.
Journal of Animal and Veterinary Advances

The present study aimed to examine whether Mycoplasma Haemofelis (MHF) and Candidatus Mycoplasma Haemominutum (CMH) occur in cats in Mainland China. Genomic DNA was extracted from 87 cat blood samples collected from Guangzhou, China and they were examined by conventional Polymerase Cham Reaction (PCR) assay to detect and distinguish infection of MHF and CMH. The total infection rate of cats with MHF and CMH was 42.5% (37/87), with one female cat being infected with MHF, while 41.4% (36/87) of the infections were due to CMH and none of the cats was positive for concurrent infection with both MHF and CMH. Sequencing of representative amplicons confirmed the results of PCR amplifications. This result, for the first time, demonstrated the existence of MHF and CMH in cats in mainland China. © Medwell Journals, 2010. Source

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