PMID: 4418576Oct 1, 1974

Induction of beta-galactosidase in Lactobacillus plantarum

Journal of Bacteriology
N Hasan, I F Durr


beta-galactosidase (beta-galactoside galactohydrolase, EC is inducible in Lactobacillus plantarum by d-galactose or thiomethyl galactoside, and to a much lesser extent by lactose, isopropyl thiomethyl galactoside, and d-fucose. Isopropyl thiomethyl galactoside is a competitive inhibitor of the enzyme with a K(i) of 4.2 mM. The K(m) of the crude enzyme for o-nitrophenyl beta-d-galactoside is 0.87 mM. Induction also requires a source of energy and amino acids. Chloramphenicol and actinomycin D inhibited induction. d-Glucose, d-fructose and to a lesser extent maltose and d-mannitol inhibited enzyme synthesis. Methyl-alpha-d-glucopyranoside was not inhibitory. Glucose exerts its effect through its ability to exclude galactose or lactose entry into the cell. The uptake of lactose and the metabolism of galactose by preinduced cells is severely inhibited by glucose. But neither galactose nor lactose severely affected the uptake of glucose by preinduced cells. Thus, glucose acts through catabolite inhibition, i.e., transport of inducer rather than repression through transcription or related mechanisms. This is supported by the inability of cyclic nucleotides to relieve the inhibition produced by glucose or to stimulate induct...Continue Reading

Related Concepts

Metabolic Process, Cellular
Anhydrous lactose
Galactose Measurement
Amino Acids, I.V. solution additive
Carbon Radioisotopes

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