从天然乳清发酵剂中分离的一株helveticus乳杆菌的β -半乳糖苷酶的分离及性质。

Journal of applied biochemistry Pub Date : 1983-08-01
M E de Macías, M C Manca de Nadra, A M Strasser de Saad, A A Pesce de Ruiz Holgado, G Oliver
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引用次数: 0

摘要

从阿根廷硬奶酪天然发酵剂中分离出一株helveticus乳杆菌,并对其性质进行了研究。酶被纯化14倍(deae -纤维素和Sepharose 6b - deae -纤维素柱层析和琼脂糖-对氨基苯基- β - d -硫代半乳糖苷亲和层析)。经聚丙烯酰胺凝胶电泳,纯化后的提取物呈单条带。在42℃、pH 6.5、50 mM磷酸盐缓冲液中观察到最大的酶活性。当pH值与最佳pH值相差很大时,观察到底物分子之间的正协同作用。邻硝基苯基半乳糖苷(ONPG)和ONPG + 10 mM乳糖的Km值分别为4.46 × 10(-5)和8.9 × 10(-5) M。葡萄糖、半乳糖、半乳糖6-磷酸和乳酸盐作为非竞争性抑制剂;MgCl2保护酶免受热变性。酶解ONPG的活化能为11,400 cal/mol。Mr估计有25万美元。它是一种低聚酶,由Mr 65000的4个亚基组成。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Isolation and properties of beta-galactosidase of a strain of Lactobacillus helveticus isolated from natural whey starter.

beta-Galactosidase has been isolated from Lactobacillus helveticus of a strain isolated from natural starters for the manufacture of Argentine hard cheeses and its properties have been studied. The enzyme was purified 14-fold (by chromatography on DEAE-cellulose and Sepharose 6B-DEAE-cellulose columns and by affinity chromatography in agarose-p-aminophenyl-beta-D-thiogalactoside). The purified extract exhibited a single band following polyacrylamide gel electrophoresis. Maximum enzymatic activity was observed at 42 degrees C and pH 6.5 in 50 mM phosphate buffer. At pH values substantially different from the optimum, a positive cooperativity between substrate molecules was observed. The Km's for o-nitrophenylgalactoside (ONPG) and ONPG + 10 mM of lactose were 4.46 X 10(-5) and 8.9 X 10(-5) M, respectively. Glucose, galactose, galactose 6-phosphate, and lactate acted as noncompetitive inhibitors; MgCl2 protected the enzyme from thermal denaturation. The activation energy of enzymatic hydrolysis of ONPG was 11,400 cal/mol. The Mr was estimated to be 250,000. It is an oligomeric enzyme made of 4 subunits of Mr 65,000.

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