UDP-GLUCOSE STEROL BETA-D-GLUCOSYLTRANSFERASE, A PLASMA MEMBRANE-BOUND ENZYME OF PLANTS - ENZYMATIC-PROPERTIES AND LIPID DEPENDENCE

被引:39
作者
ULLMANN, P [1 ]
URY, A [1 ]
RIMMELE, D [1 ]
BENVENISTE, P [1 ]
BOUVIERNAVE, P [1 ]
机构
[1] INST BOT,IBMP,UPR 406,DEPT ENZYMOL CELLULAIRE & MOLEC,28 RUE GOETHE,F-67083 STRASBOURG,FRANCE
关键词
PLANT PLASMA MEMBRANE; AFFINITY CHROMATOGRAPHY; SITE REAGENTS; PHOSPHOLIPID DEPENDENCE; UDP-GLUCOSE STEROL GLUCOSYLTRANSFERASE;
D O I
10.1016/0300-9084(93)90102-X
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
UDP-glucose sterol beta-D-glucosyltransferase (UDPG-SGTase) catalyzes the glucosylation of plant sterols. This enzyme has been shown to be membrane-bound, most of its activity being associated with plasma membrane in etiolated maize coleoptiles. After solubilization with detergents, total delipidation and purification, kinetic studies performed with a purified enzyme preparation in the presence of detergent and soybean phosphatidylcholine (PC) strongly suggest an ordered bi-bi mechanism for the glucosylation of sterols. A reduced sulfhydryl group and an arginyl residue were shown to be essential for activity. Lipid dependence studies have been performed on the delipidated enzyme in two systems: a micellar one composed of a mixture of enzyme, detergent and phospholipids and another one where the enzymatic activity was reconstituted in unilamellar lipid vesicles. In both systems it was shown that the UDPG-SGTase activity was stimulated to a large extent by negatively charged phospholipids. Enzymatic assays were performed with membrane fractions originating from plants whose sterol content was profoundly modified following treatment with a sterol biosynthesis inhibitor. Results showed that the sterol glucosylating activity was strongly inhibited in these fractions in accordance with sterol substrate specificity studies. All these results show that the UDPG-SGTase is exquisitely sensitive to its lipid environment. Physiological implications of these data are discussed in the light of the putative role of sterols in the plant cell.
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页码:713 / 723
页数:11
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