UDP-N-乙酰葡糖胺的合成底物类似物：甘露糖α1-3受体β1-2-N-乙酰葡糖胺基转移酶I。该酶的底物特异性和抑制剂。

Synthetic substrate analogues for UDP-GlcNAc: Man alpha 1-3R beta 1-2-N-acetylglucosaminyltransferase I. Substrate specificity and inhibitors for the enzyme.

作者信息

Reck F, Springer M, Meinjohanns E, Paulsen H, Brockhausen I, Schachter H

机构信息

Research Institute, Hospital for Sick Children, Toronto, Ont, Canada.

出版信息

Glycoconj J. 1995 Dec;12(6):747-54. doi: 10.1007/BF00731234.

DOI:10.1007/BF00731234

PMID:8748150

Abstract

UDP-GlcNAc:Man alpha 1-3R beta 1-2-N-acetylglucosaminyltransferase I (GlcNAc-T I; EC 2.4.1.101) catalyses the conversion of [Man alpha 1-6(Man alpha 1-3)Man alpha 1-6][Man alpha 1-3]Man beta-O-R to [Man alpha 1-6(Man alpha 1-3)Man alpha 1-6] [GlcNAc beta 1-2Man alpha 1-3]Man beta-O-R (R = 1-4GlcNAc beta 1-4GlcNAc- Asn-X) and thereby controls the conversion of oligomannose to complex and hybrid asparagine-linked glycans (N-glycans). GlcNAc-T I also catalyses the conversion of Man alpha 1-6(Man alpha 1-3)Man beta-O-octyl to Man alpha 1-6(GlcNAc beta 1-2Man alpha 1-3)Man beta-O-octyl. We have therefore tested a series of synthetic analogues of Man"alpha 1-6(Man'alpha 1-3)Man beta-O-octyl as substrates and inhibitors for rat liver GlcNAc-T I. The 2"-deoxy and the 3"-, 4"- and 6"-O-methyl derivatives are all good substrates confirming previous observations that the hydroxyl groups of the Man"alpha 1-6 residue do not play major roles in the binding of substrate to enzyme. In contrasts, all four hydroxyl groups on the Man'alpha 1-3 residue are essential since the corresponding deoxy derivatives either do not bind (2'- and 3'-deoxy) or bind very poorly (4'- and 6'-deoxy) to the enzyme. The 2'- and 3'-O-methyl derivatives also do not bind to the enzyme. However, the 4'-O-methyl derivative is a substrate (KM = 2.6 mM) and the 6'-O-methyl compound is a competitive inhibitor (Ki = 0.76 mM). We have therefore synthesized various 4'- and 6'-O-alkyl derivatives, some with reactive groups attached to an O-pentyl spacer, and tested these compounds as reversible and irreversible inhibitors of GlcNAc-T I. The 6'-O-(5-iodoacetamido-pentyl) compound is a specific time dependent inhibitor of the enzyme. Four other 6'-O-alkyl compounds showed competitive inhibition while the remaining compounds showed little or no binding indicating that the electronic properties of the attached O-pentyl groups influence binding.

摘要

UDP-N-乙酰葡糖胺：α1-3甘露糖β1-2-N-乙酰葡糖胺基转移酶I（GlcNAc-T I；EC 2.4.1.101）催化[α1-6（α1-3甘露糖）α1-6][α1-3甘露糖]甘露糖β-O-R转化为[α1-6（α1-3甘露糖）α1-6][β1-2N-乙酰葡糖胺α1-3甘露糖]甘露糖β-O-R（R = 1-4N-乙酰葡糖胺β1-4N-乙酰葡糖胺-天冬酰胺-X），从而控制低聚甘露糖向复杂型和杂合型天冬酰胺连接聚糖（N-聚糖）的转化。GlcNAc-T I还催化α1-6（α1-3甘露糖）甘露糖β-O-辛酯转化为α1-6（β1-2N-乙酰葡糖胺α1-3甘露糖）甘露糖β-O-辛酯。因此，我们测试了一系列α1-6（α1-3甘露糖）甘露糖β-O-辛酯的合成类似物作为大鼠肝脏GlcNAc-T I的底物和抑制剂。2''-脱氧和3''-、4''-及6''-O-甲基衍生物都是良好的底物，这证实了先前的观察结果，即α1-6甘露糖残基的羟基在底物与酶的结合中不起主要作用。相比之下，α1-3甘露糖残基上的所有四个羟基都是必需的，因为相应的脱氧衍生物要么不结合（2'-和3'-脱氧），要么与酶结合很差（4'-和6'-脱氧）。2'-和3'-O-甲基衍生物也不与酶结合。然而，4'-O-甲基衍生物是一种底物（KM = 2.6 mM），6'-O-甲基化合物是一种竞争性抑制剂（Ki = 0.76 mM）。因此，我们合成了各种4'-和6'-O-烷基衍生物，其中一些带有连接到O-戊基间隔基上的反应性基团，并测试了这些化合物作为GlcNAc-T I的可逆和不可逆抑制剂。6'-O-（5-碘乙酰胺基-戊基）化合物是该酶的一种特异性时间依赖性抑制剂。其他四种6'-O-烷基化合物表现出竞争性抑制，而其余化合物几乎没有或没有结合，这表明连接的O-戊基基团的电子性质影响结合。