Lee L, Forstner G
Can J Biochem Cell Biol. 1985 Apr;63(4):257-62. doi: 10.1139/o85-037.
Rat intestinal maltase-glucoamylase was purified in the presence of detergent and proteolytic inhibitors, and the 130000 and 145000 subunits were separated and isolated by preparative sodium dodecyl sulfate - polyacrylamide gel electrophoresis and electrophoretic elution. Amino acid analyses were very similar, with a small excess of apolar amino acid residues in the 145000 subunit. Peptide mapping with Staphylococcus aureus V8 protease revealed eight similar peptide products for each, with apparent elongation of the five larger peptides in the 145000 subunit by a relative mass (Mr) of 2000-5000. alpha-Chymotrypsin maps showed at least eight identical cleavage products plus one large, shared product which was larger by a Mr of 5000 in the 145000 subunit. Cyanogen bromide cleavage of the 145000 subunit produced a single peptide of Mr 75000. A peptide of Mr 66000, also indicative of a central cleavage, was generated from the 130000 subunit, but a second cleavage into 43000 and 23000 segments was also evident. Several sets of antibodies formed against both antigens consistently gave reactions of identity without spurring on immunodiffusion. These results indicate extreme homology between the central segment of the 145000 subunit and the 130000 subunit. The cyanogen bromide cleavage results suggest, however, that the two central sequences are not absolutely identical and therefore that one subunit may not be a posttranslational derivative of the other.
大鼠肠麦芽糖酶 - 葡糖淀粉酶在去污剂和蛋白水解抑制剂存在的情况下被纯化，130000和145000亚基通过制备性十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳和电泳洗脱进行分离和纯化。氨基酸分析结果非常相似，145000亚基中极性氨基酸残基略有过量。用金黄色葡萄球菌V8蛋白酶进行肽图谱分析显示，每个亚基都有八个相似的肽产物，145000亚基中五个较大的肽的相对分子质量（Mr）明显延长了2000 - 5000。α-胰凝乳蛋白酶图谱显示至少有八个相同的裂解产物，加上一个大的共享产物，该产物在145000亚基中的Mr大5000。溴化氰裂解145000亚基产生了一个Mr为75000的单一肽段。从130000亚基中产生了一个Mr为66000的肽段，也表明有中央裂解，但也明显有第二次裂解成43000和23000片段。针对两种抗原形成的几组抗体在免疫扩散中始终产生相同的反应而无刺激现象。这些结果表明145000亚基的中央片段与130000亚基之间存在极高的同源性。然而，溴化氰裂解结果表明这两个中央序列并非绝对相同，因此一个亚基可能不是另一个亚基的翻译后衍生物。
