Chiba Y, Yamagata Y, Iijima S, Nakajima T, Ichishima E
Department of Applied Biological Chemistry, Faculty of Agriculture, Tohoku University, Sendai, Japan.
Curr Microbiol. 1993 Nov;27(5):281-8. doi: 10.1007/BF01575993.
Acid carboxypeptidase from Aspergillus saitoi is a glycoprotein that contains both N- and O-linked sugar chains. The N-glycanase released high-mannose type oligosaccharides that were separated into eight components on HPLC. One, which had a unique structure of Man11GlcNAc2, was characterized. Mild alkali treatment of the carboxypeptidase, under conditions that effect beta-elimination, yielded D-mannose. Deglycosylation of the carboxypeptidase with endo-beta-N-acetylglucosaminidase and alpha-mannosidase effected the reduction of the molecular mass from 72 kDa to 60 kDa. Partial changes of CD spectra of the native and the deglycosylated enzymes indicate that some conformational changes on the peptide of the enzyme occurred after deglycosylation. Other enzymatic properties, such as catalytic activity, pH, and thermal stability and resistivity to protease digestion, did not appear to change. Tunicamycin halted secretion of the carboxypeptidase extracellularly.
来自斋藤曲霉的酸性羧肽酶是一种糖蛋白，同时含有N-连接和O-连接的糖链。N-聚糖酶释放出高甘露糖型寡糖，这些寡糖在高效液相色谱上被分离成八个组分。其中一个具有Man11GlcNAc2独特结构的组分得到了表征。在能发生β-消除反应的条件下，对羧肽酶进行温和的碱处理，产生了D-甘露糖。用内切β-N-乙酰葡糖胺酶和α-甘露糖苷酶对羧肽酶进行去糖基化处理，使分子量从72 kDa降至60 kDa。天然酶和去糖基化酶的圆二色光谱的部分变化表明，去糖基化后酶肽段发生了一些构象变化。其他酶学性质，如催化活性、pH值、热稳定性和对蛋白酶消化的抗性，似乎没有改变。衣霉素阻止了羧肽酶在细胞外的分泌。
