Journal
PROCESS BIOCHEMISTRY
Volume 48, Issue 10, Pages 1516-1523Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.procbio.2013.07.014
Keywords
Peroxidase; Cassava; Purification; Thiols; Inhibition
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Funding
- Department of Biochemistry, Program in Biotechnology, Faculty of Science and Graduate School of Chulalongkorn University
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Cassava peroxidase (CSP) isolated from cassava leaves (Manihot esculenta Crantz of cv. KU50) was purified by DEAE and concanavalin-A column chromatography. CSP was a haem-containing cationic glycoprotein with the molecular weight of 38 and 44 kDa determined by MALDI-TOF-MS. Its kinetic catalysis in the presence and absence of some thiols were investigated and compared to those of horseradish and soybean peroxidases by using urea hydrogen peroxide (UHP) and 3,3',5,5'-tetramethylbenzidine (TMB) as substrates. Inhibitory effects of some pesticides containing thiol groups such as thiosemicabazide, thiourea and thiophanate-methyl on TMB oxidation were graphically demonstrated their ability to be either competitive or noncompetitive inhibitors, depending on their properties. The degrees of inhibition were expressed as K-i and IC50 values. The applicable range for the detection of thiosemicabazide in solution was found to be in the range of 10-100 mu M, whereas those of thiourea and thiophanate-methyl were 40-400 mu M and 10-460 mu M, respectively. On the contrary, the inhibitory effects of some phenolic pollutants; 4-nitrophenol, 4-phenylphenol and pentachlorophenol on TMB oxidation were not significantly observed and the phenomenon was discussed. (C) 2013 Elsevier Ltd. All rights reserved.
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