Properties of beta-galactosidase III: implications for entry of galactosides into Klebsiella.
Klebsiella sp. strain CT-200 lacks both its plasmid-borne lac operon, which specifies beta-galactosidase I, and its chromosomal lac operon, which specifies beta-galactosidase II, but it expresses a gene for a third beta-galactosidase, beta-galactosidase III, constitutively. CT-200 was examined to determine whether there was a beta-galactoside permease associated with the beta-galactosidase III gene. The failure of CT-200 to transport thiomethyl-beta-galactoside, o-nitrophenyl-beta-D-galactopyranoside, phenyl-beta-galactoside, lactulose, or galactosyl-arabinose was taken as evidence that beta-galactoside permease is not part of a beta-galactosidase III operon. Optimal assay conditions for beta-galactosidase II, whose activity was used as a measure of beta-galactoside transport, are reported here, as are an improved purification method and some physical and catalytic properties of the enzyme not previously reported.
D001692:Biological Transport; D005696:Galactosidases / Q000235:genetics*; D005697:Galactosides / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D007526:Isoelectric Point; D007709:Klebsiella / Q000201:enzymology* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics*; D008970:Molecular Weight; D009876:Operon; D001616:beta-Galactosidase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
D005697:Galactosides; D006027:Glycosides; D026901:Membrane Transport Proteins; D005696:Galactosidases; D001616:beta-Galactosidase