Heteroglycan Synthesis in <em>Cryptococcus laurentii</em>

An enzyme preparation from catalyzes the transfer of glycosyl units from sugar nucleotides to exogenous acceptor resulting in the stepwise synthesis of a heteroglycan with the following structure: 2--α-d-mannosyl-6--α-d-mannosyl-3--α-d-mannosyl-(2--β-d-xylosyl-)-d-mannose. The same enzyme preparation transfersd-[14C]-mannosyl from GDP [14C]mannose to an endogenous glycoprotein acceptor. Analysis of the endogenous product after mild acid hydrolysis revealed the presence of Man-2-mannose, Man-3-mannose, and Man-6-mannose. The enzymes synthesizing the specific mannosyl linkages in the pentasaccharide have been shown to be distinct mannosyl-transferases (Schutzbach, J. S.,andAnkel, H. (1971) 246, 2187–2194). The β-xylosyl linkage in the pentasaccharide is made by an enzyme that also transfers xylose from UDP-xylose to the same endogenous acceptor (Schutzbach, J. S.,andAnkel, H. (1972) 247, 6574–6580). Glycosyl transfer to exogenous and to endogenous acceptors appears to involve the same enzymes, suggesting that the pentasaccharide synthesized is an integral part of the cell envelope glycoprotein.

一种来自[某种生物或组织，原文缺失]的酶制剂催化糖基单元从糖核苷酸向外源受体的转移，从而逐步合成具有以下结构的杂聚糖：2 - -α - D - 甘露糖基 - 6 - -α - D - 甘露糖基 - 3 - -α - D - 甘露糖基 - (2 - -β - D - 木糖基 - ) - D - 甘露糖。相同的酶制剂将D - [14C] - 甘露糖基从GDP - [14C]甘露糖转移至一种内源性糖蛋白受体。温和酸水解后对内源性产物的分析显示存在Man - 2 - 甘露糖、Man - 3 - 甘露糖和Man - 6 - 甘露糖。在五糖中合成特定甘露糖基连接的酶已被证明是不同的甘露糖基转移酶（舒茨巴赫，J. S.，和安克尔，H.（1971年）《[期刊名缺失]》246，2187 - 2194）。五糖中的β - 木糖基连接是由一种酶形成的，该酶也将木糖从UDP - 木糖转移至相同的内源性受体（舒茨巴赫，J. S.，和安克尔，H.（1972年）《[期刊名缺失]》247，6574 - 6580）。糖基向外源和内源性受体的转移似乎涉及相同的酶，这表明合成的五糖是细胞膜糖蛋白的一个组成部分。