Manzella S M, Rodén L, Meezan E
Department of Pharmacology, University of Alabama at Birmingham 35294, USA.
Glycobiology. 1995 Mar;5(2):263-71. doi: 10.1093/glycob/5.2.263.
Glycogenin is the core protein of glycogen proteoglycan and is, at the same time, a self-glucosylating enzyme which catalyses early glucosyl transfer steps in the biosynthesis of glycogen. In the course of this process, glycogenin is glucosylated progressively until an oligosaccharide containing 8-11 glucose residues has been formed. Although glycogenin, under physiological conditions, is both enzyme and acceptor in the glucosyl transfer reactions, it is also capable of utilizing p-nitrophenyl-linked malto-oligosaccharides as exogenous acceptors. In view of the potential usefulness of exogenous acceptors in the study of the mechanism of the glycogenin reaction, we have expanded the search for such compounds and report here that several alkyl glucosides and alkyl maltosides may serve as acceptors in glucosyl transfer by beef kidney glycogenin. Dodecyl-beta-D-maltoside (Km approximately 100 microM) was the most effective acceptor among the compounds tested and yielded 30 times as much product as p-nitrophenyl-alpha-maltoside. Substantial product formation was also observed with tetradecyl-beta-D-maltoside and octyl-beta-D-maltoside (39 and 22%, respectively, of the value measured for dodecyl-beta-D-maltoside). It was further demonstrated that dodecyl-beta-D-maltoside served as an acceptor in the transfer of xylose from UDP-xylose, indicating that the exogenous substrate behaved similarly to glycogenin itself in this regard. Dodecyl-beta-D-maltoside has already proven useful in the development of a simple glycogenin assay, and it is further suggested that this and related compounds may be active in vivo and in cell culture as artificial initiators of glycogen synthesis.
糖原素是糖原蛋白聚糖的核心蛋白，同时也是一种自我糖基化酶，它催化糖原生物合成中早期的糖基转移步骤。在此过程中，糖原素逐渐被糖基化，直到形成含有8 - 11个葡萄糖残基的寡糖。尽管在生理条件下，糖原素在糖基转移反应中既是酶又是受体，但它也能够利用对硝基苯基连接的麦芽寡糖作为外源受体。鉴于外源受体在糖原素反应机制研究中的潜在用途，我们扩大了对此类化合物的搜索，并在此报告几种烷基糖苷和烷基麦芽糖苷可作为牛肾糖原素糖基转移的受体。在所测试的化合物中，十二烷基 - β - D - 麦芽糖苷（Km约为100 microM）是最有效的受体，其产生的产物是对硝基苯基 - α - 麦芽糖苷的30倍。用十四烷基 - β - D - 麦芽糖苷和辛基 - β - D - 麦芽糖苷也观察到了大量产物形成（分别为十二烷基 - β - D - 麦芽糖苷测量值的39%和22%）。进一步证明，十二烷基 - β - D - 麦芽糖苷在木糖从UDP - 木糖的转移中作为受体，表明在这方面外源底物的行为与糖原素本身相似。十二烷基 - β - D - 麦芽糖苷已被证明在开发一种简单的糖原素测定方法中有用，并且进一步表明这种及相关化合物在体内和细胞培养中可能作为糖原合成的人工引发剂具有活性。
