Eoyang L, Silverman P M
J Bacteriol. 1984 Jan;157(1):184-9. doi: 10.1128/jb.157.1.184-189.1984.
Acetohydroxyacid synthase I from Escherichia coli K-12 has been purified to near homogeneity. Analysis of the purified enzyme by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the presence of two polypeptides, one with a molecular weight of 60,000 and one with a molecular weight of 9,500. These two polypeptides were present in constant proportion to each other and to enzyme activity. The molar ratio of the two polypeptides (Mr 9,500:60,000), estimated from stained polyacrylamide gels, was 1. Antisera raised against the 60,000 Mr polypeptide precipitated both the 60,000 and the 9,500 Mr polypeptides from extracts of cells labeled with [35S]methionine. The addition of sodium dodecyl sulfate before immunoprecipitation eliminated the smaller polypeptide, and only the larger one was recovered. The hydrodynamic properties of the native enzyme confirmed a previous report that the largest enzymatically active species has a molecular weight of about 200,000; this species contains both the 60,000- and 9,500-molecular-weight polypeptides.
来自大肠杆菌K-12的乙酰羟酸合酶I已被纯化至接近均一。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳对纯化后的酶进行分析，结果显示存在两种多肽，一种分子量为60,000，另一种分子量为9,500。这两种多肽彼此之间以及与酶活性的比例恒定。从染色的聚丙烯酰胺凝胶估计，这两种多肽的摩尔比（Mr 9,500:60,000）为1。针对60,000 Mr多肽产生的抗血清从用[35S]甲硫氨酸标记的细胞提取物中沉淀出了60,000和9,500 Mr的多肽。在免疫沉淀前加入十二烷基硫酸钠可去除较小的多肽，仅回收较大的多肽。天然酶的流体动力学性质证实了先前的一份报告，即最大的具有酶活性的物种分子量约为200,000；该物种同时包含分子量为60,000和9,500的多肽。
