Watanabe K
J Biochem. 1976 Aug;80(2):379-87. doi: 10.1093/oxfordjournals.jbchem.a131287.
Mild alkaline treatment of glycopeptide (GP-II) resulted in the loss of 1 mole of serine and 5 moles of threonine per mole of GP-II, suggesting the presence of O-glycosyl bonds between 1 serine and 5 threonine residues and carbohydrate chains. Treatment of GP-II with alkaline borohydride released only disaccharide. Methylation studies of the carbohydrate moiety gave 2,3,4,6-tetra-O-methyl and 2,4,6-tri-O-methyl derivatives of mannose in a ratio of approximately 1:1. In addition, one step of Smith degradation resulted in the loss of about 6 residues of mannose per mole of GP-II. Moreover, alpha-mannosidase [EC 3.2.1.24] liberated about 6 residles of mannose per mole of GP-II. On the basis of these data, the structure of the carbohydrate moiety of GP-II was confirmed to be 3-O-alpha-mannosylmannose. The amino- and carboxyl-terminal amino acids of GP-II were determined to be threonine and serine, respectively. On reductive cleavage of N-proline bonds with metallic sodium in liquid ammonia, 2 moles of alanine per mole of GP-II were lost. From the compositions of three fragments isolated from the reductive cleavage products, the amino acid sequence of the peptide portion of GP-II was determined. Based on these data, a probable structure was proposed for GP-II.
对糖肽（GP-II）进行轻度碱性处理后，每摩尔GP-II损失1摩尔丝氨酸和5摩尔苏氨酸，这表明在1个丝氨酸和5个苏氨酸残基与碳水化合物链之间存在O-糖基键。用碱性硼氢化钠处理GP-II仅释放出二糖。对碳水化合物部分的甲基化研究得到了比例约为1:1的甘露糖的2,3,4,6-四-O-甲基和2,4,6-三-O-甲基衍生物。此外，一步Smith降解导致每摩尔GP-II损失约6个甘露糖残基。而且，α-甘露糖苷酶[EC 3.2.1.24]每摩尔GP-II释放出约6个甘露糖残基。基于这些数据，确认GP-II碳水化合物部分的结构为3-O-α-甘露糖基甘露糖。GP-II的氨基末端和羧基末端氨基酸分别确定为苏氨酸和丝氨酸。在液氨中用金属钠对N-脯氨酸键进行还原裂解时，每摩尔GP-II损失2摩尔丙氨酸。根据从还原裂解产物中分离出的三个片段的组成，确定了GP-II肽部分的氨基酸序列。基于这些数据，提出了GP-II的可能结构。
