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首页> 外文OA文献 >Characterization of Two New Glycosyl Hydrolases from the Lactic Acid Bacterium Carnobacterium piscicola Strain BA
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Characterization of Two New Glycosyl Hydrolases from the Lactic Acid Bacterium Carnobacterium piscicola Strain BA

机译：乳酸杆菌食肉芽孢杆菌菌株BA的两个新的糖基水解酶的表征

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Three genes with homology to glycosyl hydrolases were detected on a DNA fragment cloned from a psychrophilic lactic acid bacterium isolate, Carnobacterium piscicola strain BA. A 2.2-kb region corresponding to an α-galactosidase gene, agaA, was followed by two genes in the same orientation, bgaB, encoding a 2-kb β-galactosidase, and bgaC, encoding a structurally distinct 1.76-kb β-galactosidase. This gene arrangement had not been observed in other lactic acid bacteria, including Lactococcus lactis, for which the genome sequence is known. To determine if these sequences encoded enzymes with α- and β-galactosidase activities, we subcloned the genes and examined the enzyme properties. The α-galactosidase, AgaA, hydrolyzes para-nitrophenyl-α-d-galactopyranoside and has optimal activity at 32 to 37°C. The β-galactosidase, BgaC, has an optimal activity at 40°C and a half-life of 15 min at 45°C. The regulation of these enzymes was tested in C. piscicola strain BA and activity on both α- and β-galactoside substrates decreased for cells grown with added glucose or lactose. Instead, an increase in activity on a phosphorylated β-galactoside substrate was found for the cells supplemented with lactose, suggesting that a phospho-galactosidase functions during lactose utilization. Thus, the two β-galactosidases may act synergistically with the α-galactosidase to degrade other polysaccharides available in the environment.
机译：在从嗜酸性乳酸菌分离株Piscicola菌株BA克隆的DNA片段上检测到三个与糖基水解酶同源的基​​因。对应于α-半乳糖苷酶基因agaA的2.2 kb区域，后面是两个方向相同的基因，分别是bgaB和2gab，BgaB编码2 kbβ-半乳糖苷酶，bgaC编码结构不同的1.76 kbβ-半乳糖苷酶。在其他乳酸菌（包括乳酸乳球菌）中尚未观察到这种基因排列，其基因组序列是已知的。为了确定这些序列是否编码具有α-和β-半乳糖苷酶活性的酶，我们将这些基因亚克隆并检查了酶的特性。 α-半乳糖苷酶AgaA水解对硝基苯基-α-d-吡喃半乳糖苷，在32至37°C时具有最佳活性。 β-半乳糖苷酶BgaC在40°C时具有最佳活性，在45°C时具有15分钟的半衰期。这些酶的调节已在C. piscicola菌株BA中进行了测试，并且对于添加了葡萄糖或乳糖的细胞而言，α-和β-半乳糖苷底物的活性均降低。相反，发现补充乳糖的细胞在磷酸化的β-半乳糖苷底物上的活性增加，表明磷酸半乳糖苷酶在乳糖利用期间起作用。因此，两个β-半乳糖苷酶可以与α-半乳糖苷酶协同作用，以降解环境中可用的其他多糖。

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