Functional Identification of a Putative ¦Â-Galactosidase Gene in the Special lac Gene Cluster of Lactobacillus?acidophilus

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• 作者：Qu Pan ; Junmin Zhu ; Lina Liu ; Yanguang Cong ; Fuquan Hu ; Jinchuan Li and Xiaoping Yu
• 刊名：Current Microbiology
• 出版年：2010
• 出版时间：March, 2010
• 年：2010
• 卷：60
• 期：3
• 页码：172-178
• 全文大小：294.5 KB

文摘

The putative β-galactosidase gene (lacZ) of Lactobacillus acidophilus has a very low degree of homology to the Escherichia coli β-galactosidase gene (lacZ) and locates in a special lac gene cluster which contains two β-galactosidase genes. No functional characteristic of the putative β-galactosidase has been described so far. In this study, the lacZ gene of L. acidophilus was hetero-expressed in E. coli and the recombinant protein was purified by a three-step procedure. The product of the lacZ gene was also extracted from L. acidophilus ATCC 4356 and active staining was carried out. The enzymatic properties of the purified recombinant LacZ were assayed. The results of hetero-expression showed the recombinant LacZ without tag had β-galactosidase activity. The purified recombinant LacZ had a specific activity of 43.2 U/mg protein. The result of active staining showed that the functional product of the lacZ gene did exist in L. acidophilus. The L. acidophilus β-galactosidase (LacZ) had an optimal pH of 6, an optimal temperature of 37¡ãC and could hydrolyze 73 % of lactose in milk in 30 h at 10¡ãC. The L. acidophilus β-galactosidase (LacZ) was identified as cold-adapted β-galactosidase in this study for the first time, and may be useful for lactose removal from dairy products at low temperatures.