Studies on glycoproteins XII. About glycosidic-ester linkages in submaxillary gland glycoproteins prepared from sheep

J.S. Best, V.P. Bhavanandan, A. Gottschalk
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引用次数: 9

Abstract

OSM prepared from sheep is known to contain O-glycosidic linkages involving the reducing group of N-acetylgalactosamine and the hydroxyl groups of serine and threonine. It is the aim of this paper to establish whether or not in addition to this linkage another type of alkali-labile linkage, in particular a glycosidic-ester linkage, is present in OSM.

In the first set of experiments it was found that the release of 35.2% of N-acetylgalactosamine, when OSM was kept at pH 8.0 and 42° for 120 h, was matched by the loss of an equimolar amount of serine and threonine without a significant change in the other amino acids. In a second set of experiments it was shown that on treating OSM with 0.1 N NaOH at 4° the decrease of bound hexosamine with time was linear. Finally, glycopeptides prepared by trypsin (EC 3.4.4.4) or pronase action on OSM were treated with LiBH4 in tetrahydrofuran. No significant difference in the dicarboxylic amino acids before and after such treatment was observed. Only traces of homoserine and α-amino-δ-hydroxy-n-valeric acid were detectable after LiBH4 reduction.

Since the LiBH4 treatment of trypsinized OSM prepared from Australian sheep resulted in the loss of 35% of the dicarboxylic acid content, the suggestion is made that the fine structure of the ovine submaxillary glycoproteins may vary with the age of the animals. In Australia, lambs of an average age of 4 months were used for the work; in Europe only sheep of three years or more are slaughtered. Similar differences with age have been described for the fine structure of the chondroitin sulphates composing human hyaline cartilage.

糖蛋白的研究羊颌下腺糖蛋白中糖苷-酯键的研究
已知从绵羊中制备的OSM含有o -糖苷键,涉及n -乙酰半乳糖胺的还原基和丝氨酸和苏氨酸的羟基。本文的目的是确定除了这种键外,OSM中是否存在另一种碱不稳定的键,特别是糖苷-酯键。在第一组实验中发现,当OSM在pH 8.0和42°下保持120 h时,n -乙酰半乳糖胺的释放量为35.2%,与之匹配的是等量的丝氨酸和苏氨酸的损失,而其他氨基酸没有明显变化。第二组实验表明,用0.1 N NaOH在4°温度下处理OSM时,结合的己糖胺随时间呈线性下降。最后,用LiBH4在四氢呋喃中处理由胰蛋白酶(EC 3.4.4.4)或pronase作用于OSM制备的糖肽。处理前后二羧基氨基酸含量无显著差异。LiBH4还原后仅检测到微量的高丝氨酸和α-氨基-δ-羟基-n-戊酸。由于对澳大利亚羊胰蛋白酶化OSM进行LiBH4处理,导致其二羧酸含量下降35%,这表明绵羊上颌下糖蛋白的精细结构可能随动物年龄的变化而变化。在澳大利亚,平均4个月大的羔羊被用于这项工作;在欧洲,只有3岁以上的羊才会被宰杀。组成人体透明软骨的硫酸软骨素的精细结构也有类似的年龄差异。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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