title: A third beta-galactosidase in a strain of Klebsiella that possesses two lac genes.
abstract: Klebsiella strain RE1544 contains two lac operons, one on the chromosome and one on a lac plasmid. A mutant of RE1544, in which the lacZ genes of both operons produce no active enzyme, was found to synthesize a beta-galactosidase that hydrolyzes ortho-nitrophenyl-beta-D-galactopyranoside but not lactose. Synthesis of this beta-galactosidase (BGase-III) is induced by lactose but not by isopropyl-1-thio-beta-D-galactopyranoside or methyl-beta-D-thiogalactopyranoside. In both the regulation of synthesis and substrate specificity, BGase-III strongly resembles the ebg0 enzyme of Escherichia coli. Nevertheless, by the criteria of immunological cross-reactivity and subunit molecular weight, BGase-III is not related to the ebg0 enzyme.
mesh_terms: D003429:Cross Reactions; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology; D005696:Galactosidases / Q000096:biosynthesis*; D005796:Genes; D006868:Hydrolysis; D007709:Klebsiella / Q000201:enzymology* / Q000235:genetics; D007785:Lactose / Q000378:metabolism*; D007786:Lactose Factors; D008970:Molecular Weight; D009154:Mutation; D009598:Nitrophenylgalactosides / Q000378:metabolism; D010957:Plasmids; D001616:beta-Galactosidase / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism
chemical_list: D009598:Nitrophenylgalactosides; D005696:Galactosidases; D001616:beta-Galactosidase; D007785:Lactose