Netherlands Institute for Dairy Research, 6710 BA Ede, The Netherlands.
Appl Environ Microbiol. 1987 Mar;53(3):577-83. doi: 10.1128/aem.53.3.577-583.1987.
A membrane-bound l-alpha-glutamyl (aspartyl)-peptide hydrolase (aminopeptidase A) (EC 3.4.11.7) from Streptococcus cremoris HP has been purified to homogeneity. The free gamma-carboxyl group rather than the amino group of the N-terminal l-alpha-glutamyl (aspartyl) residue appeared to be essential for catalysis. No endopeptidase activity could be established with this enzyme. The native enzyme is a polymeric, most probably trimeric, metalloenzyme (relative molecular weight, approximately 130,000) which shows on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels apparent high relative molecular weight values due to (lipid?) material dissociable with butanol. The subunit (relative molecular weight, approximately 43,000) is catalytically inactive. The enzyme is inactivated completely by dithiothreitol, chelating agents, and the bivalent metal ions Cu and Hg. Of the sulfhydryl-blocking reagents tested, only p-hydroxymercuribenzoate appeared to inhibit the enzyme. Activity lost by treatment with a chelating agent could be restored by Co and Zn. The importance of the occurrence of an aminopeptidase A in S. cremoris with respect to growth in milk is discussed.
从嗜热链球菌 HP 中纯化出一种膜结合的 l-α-谷氨酰（天冬氨酰）-肽水解酶（氨肽酶 A）（EC 3.4.11.7）。游离的 γ-羧基而不是 N-末端 l-α-谷氨酰（天冬氨酰）残基的氨基似乎对催化是必需的。该酶没有内肽酶活性。天然酶是一种聚合的，很可能是三聚体，金属酶（相对分子质量约为 130000），由于与丁醇可分离的（脂质？）物质，在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳凝胶中显示出明显的高相对分子质量值。亚基（相对分子质量约为 43000）无催化活性。该酶被二硫苏糖醇、螯合剂和二价金属离子 Cu 和 Hg 完全失活。在所测试的巯基阻断试剂中，只有对羟基汞苯甲酸似乎抑制了该酶。用螯合剂处理失去的活性可以通过 Co 和 Zn 恢复。讨论了嗜热链球菌中氨肽酶 A 的存在对牛奶中生长的重要性。
