Product formation and phosphoglucomutase activities in Lactococcus lactis: cloning and characterization of a novel phosphoglucomutase gene

• Published in: Microbiology (Society for General Microbiology) Vol. 143; no. 3; pp. 855 - 865
• Main Authors: Qian, Ny, Stanley, Grant A, Bunte, Annicka, Radstrom, Peter
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.03.1997; Society for General Microbiology
• Subjects: Amino Acid Sequence; Bacteriology; Base Sequence; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Cloning, Molecular; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Bacterial; Genetics; Lactococcus lactis; Lactococcus lactis - enzymology; Lactococcus lactis - genetics; Microbiology; Mission oriented research; Molecular Sequence Data; Phosphoglucomutase - genetics; Sequence Alignment; Lactococcus lactis; Lactic acid bacteria; Nucleotide sequence; Enzyme; β-Phosphoglucomutase; Maltose; Gene expression; Metabolism; Streptococcaceae; Regulation(control); Isomerases; Enzymatic activity; DNA; Intramolecular transferases; Bacteria; Micrococcales; Phosphotransferases; Aminoacid sequence
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/00221287-143-3-855

1 Department of Applied Microbiology, Lund Institute of Technology, Lund University, PO Box 124, S-221 00 Lund, Sweden 2 Department of Food Technology, Victoria University, PO Box 14428, MCMC Melbourne, Victoria 8001, Australia ABSTRACT Maltose metabolism in Lactococcus lactis involves the conversion of β-glucose 1-phosphate to glucose 6-phosphate, a reaction which is reversibly catalysed by a maltose-inducible and glucose-repressible β-phosphoglucomutase (β-PGM). The gene encoding β-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 expressed a polypeptide with a calculated molecular mass of 24210 Da, which is in agreement with the molecular mass of the purified β-PGM (25 kDa). A short sequence at the N-terminus was found to be similar to known metal-binding domains. The expression of β-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 β-PGM does not serve solely to degrade maltose, but that it is also involved in the metabolism of other carbohydrates. The specific activity of -PGM during fermentation was dependent on the maltose concentration in the medium. The maximum specific activity of β-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 I -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 β-PGM responded similarly to β-PGM, but the magnitude of the response was lower. Preferential sugar utilization and - and β-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. * Author for correspondence: Peter Rådström. Tel: + 46 46 2223412. Fax: +46 46 2224203. e-mail: Peter.Radstrom@tmb.lth.se Keywords: β-phosphoglucomutase, Lactococcus lactis, maltose, metabolism