Pontarolo R, Duarte J H, Feijó M A
Departamento de Farmácia, Universidade Federal do Paraná, Brazil.
Placenta. 1993 Jul-Aug;14(4):439-48. doi: 10.1016/s0143-4004(05)80464-3.
Polysaccharides were extracted from 8-month-old placenta with aqueous HgCl2. The protein-free material was purified by selective precipitation with Cetavlon in the presence of sodium borate at pH 8.5 and was homogeneous on molecular-sieve chromatography, electrophoresis, and on treatment with Concanavalin A. The preparation contained galactose and glucose as principal monosaccharides with 5 per cent of hexosamines. Methylation studies suggested that D-gluco and D-galactopyranosyl units may be constituents of glucan and galactan respectively which form a molecular aggregate that does not dissociate during the fractionation procedures. After treatment of the fraction with beta-amylase, the proportion of glucose in the polysaccharide diminished, indicating the presence of (1-->4)-linked alpha-D-glucopyranosyl residues. Also, when the fraction was treated with a crude protease having glucosidase activity a residual alpha-D-galactopyranan was isolated and found to contain non-reducing end-groups (30.0 per cent), 3-O-(39.5 per cent) and 3,6-di-O-substituted (30.5 per cent) units. The structure of the galactan was not modified according to methylation data, on removal of the glucosyl component. The polysaccharide fraction (pH 8.5 Cetavlon), isolated from bovine placenta, thus contains a glycogen-like material associated with a galactan as molecular aggregate. This galactan has not been previously recognized in bovine placenta and its occurrence in this organ supports the hypothesis that galactose-containing polysaccharides are involved in foetal development.
用氯化汞水溶液从8个月大的胎盘提取多糖。在pH 8.5的硼酸钠存在下，通过十六烷基三甲基溴化铵选择性沉淀法对无蛋白物质进行纯化，该物质在分子筛色谱、电泳以及用伴刀豆球蛋白A处理时均呈均一状态。该制剂主要的单糖成分为半乳糖和葡萄糖，还有5%的己糖胺。甲基化研究表明，D-葡萄糖和D-吡喃半乳糖基单元可能分别是葡聚糖和半乳聚糖的组成部分，它们形成一种分子聚集体，在分级分离过程中不会解离。用β-淀粉酶处理该级分后，多糖中葡萄糖的比例降低，表明存在(1→4)-连接的α-D-吡喃葡萄糖基残基。此外，当用具有葡萄糖苷酶活性的粗蛋白酶处理该级分时，分离出一种残留的α-D-吡喃半乳聚糖，发现其含有非还原端基（30.0%）、3-O-（39.5%）和3,6-二-O-取代（30.5%）单元。根据甲基化数据，去除葡糖基成分后，半乳聚糖的结构未发生改变。因此，从牛胎盘中分离出的多糖级分（pH 8.5十六烷基三甲基溴化铵）含有一种与半乳聚糖以分子聚集体形式存在的类糖原物质。这种半乳聚糖以前在牛胎盘中未被识别，它在该器官中的存在支持了含半乳糖多糖参与胎儿发育的假说。
