EFFECT OF BROMOCONDURITOL ON GLUCOSIDASE-II FROM RAT-LIVER - A NEW KINETIC-MODEL FOR THE BINDING AND HYDROLYSIS OF THE SUBSTRATE

被引:30
作者
ALONSO, JM [1 ]
SANTACECILIA, A [1 ]
CALVO, P [1 ]
机构
[1] UNIV LEON,DEPT BIOQUIM & BIOL MOLEC,E-24007 LEON,SPAIN
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1993年 / 215卷 / 01期
关键词
D O I
10.1111/j.1432-1033.1993.tb18004.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
Bromoconduritol inhibits the p-nitrophenyl-glucosidase and maltase activities of glucosidase II purified from rat liver, an enzyme that removes the two alpha-1,3-linked glucose residues of the protein-bound oligosaccharide Glc2Man9GlcNAc2 in the processing of N-glycoproteins. The inactivation process exhibits pseudo-first-order kinetics. Previously, we have demonstrated the ocurrence of two binding (active) sites in the glucosidase II for the substrates p-nitrophenyl alpha-D-glucopyranoside (pNphGlc) and maltose (high- and low-affinity sites). The inhibition kinetic studies with bromo-conduritol indicate that the high- and low-affinity sites for pNphGlc correspond to high- and low-affinity sites for maltose, respectively. Bromoconduritol has no effect on the binding of the substrates (pNphGlc and maltose) to the high-affinity site, although it does modify the low-affinity site and hinders the binding of the two indicated substrates to this site. These results, together with previous reports, have prompted us to propose a new kinetic model of binding and hydrolysis of the physiological substrate of the enzyme, in which the outermost glucose residue would bind and be released at the high-affinity site, whereas the innermost glucose residue would do so at the low-affinity site.
引用
收藏
页码:37 / 42
页数:6
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