Product formation and phosphoglucomutase activities in Lactococcus lactis: Cloning and characterization of a novel phosphoglucomutase gene
Product formation and phosphoglucomutase activities in Lactococcus lactis: Cloning and characterization of a novel phosphoglucomutase gene
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DOI：
10.1099/00221287-143-3-855
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发表时间：
1997-03-01
期刊：
影响因子：
2.8
通讯作者：
Radstrom, P
中科院分区：
文献类型：
--
作者：
Qian, N;Stanley, GA;Radstrom, P
乳酸乳球菌中的麦芽糖代谢涉及β-葡萄糖1-磷酸转化为葡萄糖6-磷酸，这是一种由麦芽糖诱导型和葡萄糖抑制型β-磷酸葡萄糖变位酶（β-PGM）可逆催化的反应。从L.用抗体检测乳酸。测定了5695 bp片段的核苷酸序列，发现了包括pgmB基因在内的6个ORF。基因技术，维多利亚表达的多肽的计算分子量为24210 Da，这与纯化的β-PGM的分子量（25 kDa）一致。发现N-末端的短序列与已知的金属结合结构域相似。β-PGM在L.发现乳酸菌也被海藻糖和蔗糖诱导，并被生长培养基中的乳糖抑制。这表明β-PGM不仅用于降解麦芽糖，而且还参与其他碳水化合物的代谢。发酵过程中β-PGM的比活性取决于培养基中麦芽糖的浓度。当麦芽糖浓度从0.8升到11.0 g l（-1）时，β-PGM的最大比活性增加了4.6倍，比生长速率增加了7倍。此外，当培养基中的初始麦芽糖浓度增加时，观察到相对于甲酸盐、乙酸盐和乙醇产生更高量的乳酸盐。α-PGM的比活性响应类似于β-PGM，但响应的幅度较低。当L.乳酸菌在葡萄糖和麦芽糖或乳糖和麦芽糖的底物组合上生长;麦芽糖是最不优选的糖。相反，半乳糖和麦芽糖被同时利用，并且在整个发酵过程中两种PGM活性都很高。
Maltose metabolism in Lactococcus lactis involves the conversion of beta-glucose 1-phosphate to glucose 6-phosphate, a reaction which is reversibly catalysed by a maltose-inducible and glucose-repressible beta-phosphoglucomutase (beta-PGM). The gene encoding beta-PGM (pgmB) was cloned from a genomic library of L. lactis using antibodies. The nucleotide sequence of a 5695 bp fragment was determined and six ORFs, including the pgmB gene, were found, The gene Technology, Victoria expressed a polypeptide with a calculated molecular mass of 24210 Da, which is in agreement with the molecular mass of the purified beta-PGM (25 kDa). A short sequence at the N-terminus was found to be similar to known metal-binding domains. The expression of beta-PGM in L. lactis was found to be induced also by trehalose and sucrose, and repressed by lactose in the growth medium. This indicates that beta-PGM does not serve solely to degrade maltose, but that it is also involved in the metabolism of other carbohydrates. The specific activity of beta-PGM during fermentation was dependent on the maltose concentration in the medium. The maximum specific activity of beta-PGM increased by a factor of 4.6, and the specific growth rate by a factor of 7, when the maltose concentration was raised from 0.8 to 11.0 g l(-1). Furthermore, a higher amount of lactate produced relative to formate, acetate and ethanol was observed when the initial maltose concentration in the medium was increased. The specific activity of alpha-PGM responded similarly to beta-PGM, but the magnitude of the response was lower. Preferential sugar utilization and alpha- and beta-PGM suppression was observed when L. lactis was grown on the substrate combinations glucose and maltose, or lactose and maltose; maltose was the least-preferred sugar, In contrast, galactose and maltose were utilized concurrently and both PGM activities were high throughout the fermentation.