Effect of Castanospermine and Related Polyhydroxyalkaloids on Purified Myrosinase from Lepidium sativum Seedlings
- 1 May 1989
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 90 (1) , 48-52
- https://doi.org/10.1104/pp.90.1.48
Abstract
Myrosinase (.beta.-thioglucoside glucohydrolase, EC 3.2.3.1) was purified to apparent homogeneity from light-grown cress (Lepidium sativum L.) seedlings. This enzyme, which catalyzes hydrolysis of the glucosinolate sinigrin (Km, 115 micromolar) at an optimum pH of 5.5 in sodium citrate buffer, had a native molecular weight of 130 .+-. 5 kilodaltons and an isoelectric point of 4.7 to 4.9 SDS-PAGE revealed two polypeptides with molecular weights of 62 and 65 kilodaltons. Both subunits contained carbohydrate as shown by periodic acid-Schiff staining. The purified enzyme hydrolyzed p-nitrophenyl-.beta.-D-glucoside (Km, 2.0 millimolar) at an optimum pH of 6.5 in phosphate buffer. The indolizidine alkaloid castanospermine, a known inhibitor of O-glycosidases, competitively inhibited the hydrolyses of sinigrin (thioglucosidase activity) and p-nitrophenyl-.beta.-D-glucoside (O-glucosidase activity) with Ki values of 5 and 6 micromolar, respectively. In contrast, the related polyhydroxyalkaloids swainsonine and deoxynojirimycin were without effect upon these hydrolyses.This publication has 17 references indexed in Scilit:
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