Wilson I B H
Institut für Chemie der Universität für Bodenkultur, Muthgasse 18, 1190 Wien, Austria.
Cell Mol Life Sci. 2004 Apr;61(7-8):794-809. doi: 10.1007/s00018-003-3278-2.
In a journey lasting 40 years from the first reports on its activity in the 1960s to its purification and the cloning of relevant complementary DNAs, peptide O-xylosyltransferase has finally arrived at the same point as many other enzymes. This enzyme, whose systematic name is UDP-alpha-D-xylose:proteoglycan core protein beta-D-xylosyltransferase (EC 2.4.2.26), catalyses the first step in the biosynthesis of chondroitin, dermatan and heparan sulphates in the endoplasmic reticulum and/or the cis-Golgi cisternae. Analyses of their primary structure show that peptide O-xylosyltransferases are members of glycosyltransferase family 14 and so are homologous to beta1,6- N-acetylglucosaminyltransferases involved in O-glycan and poly- N-acetyllactosamine branching. Furthermore, vertebrates appear to have two rather similar genes encoding xylosyltransferase I and xylosyltransferase II, but enzymatic activity was only detected for a recombinant form of the first isoform. On the other hand, Caenorhabditis and Drosophila have each only one peptide O-xylosyltransferase gene. In the worm sqv-6 mutant, a mutation of the xylosyltransferase gene is associated with defective vulval morphogenesis, indicative of the importance of the glycosaminoglycan chains of proteoglycans in animal development. There remain, however, open questions, for instance, on the enzyme's intracellular localisation and structure-function relationships.
从20世纪60年代首次报道其活性，到其纯化以及相关互补DNA的克隆，肽O-木糖基转移酶历经40年的历程，终于走到了与许多其他酶相同的阶段。这种酶的系统名称是UDP-α-D-木糖：蛋白聚糖核心蛋白β-D-木糖基转移酶（EC 2.4.2.26），它催化内质网和/或顺式高尔基体潴泡中硫酸软骨素、硫酸皮肤素和硫酸乙酰肝素生物合成的第一步。对其一级结构的分析表明，肽O-木糖基转移酶是糖基转移酶家族14的成员，因此与参与O-聚糖和聚N-乙酰乳糖胺分支的β1,6-N-乙酰葡糖胺基转移酶同源。此外，脊椎动物似乎有两个相当相似的基因分别编码木糖基转移酶I和木糖基转移酶II，但仅在第一种同工型的重组形式中检测到酶活性。另一方面，秀丽隐杆线虫和果蝇各自只有一个肽O-木糖基转移酶基因。在蠕虫sqv-6突变体中，木糖基转移酶基因的突变与外阴形态发生缺陷有关，这表明蛋白聚糖的糖胺聚糖链在动物发育中的重要性。然而，仍然存在一些未解决的问题，例如，关于该酶的细胞内定位以及结构-功能关系。
