title: Site-directed mutagenic replacement of glu-461 with gln in beta-galactosidase (E. coli): evidence that glu-461 is important for activity.
abstract: Glutamic acid 461 of beta-galactosidase (E. coli) was replaced by gln using site-directed mutagenesis. Kinetic studies on the purified Q461-beta-galactosidase showed that it had less than 0.4% of the wild-type activity (with ONPG as substrate), confirming other studies which have suggested that the negative charge on glu-461 is important for activity. The Km values did not increase, indicating that binding of the substrate was not decreased by this change. Thermal denaturation studies showed Q461-beta-galactosidase to be somewhat more susceptible to heat denaturation than the wild-type enzyme.
mesh_terms: D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005696:Galactosidases / Q000235:genetics*; D005971:Glutamates; D018698:Glutamic Acid; D005973:Glutamine; D007700:Kinetics; D013329:Structure-Activity Relationship; D013696:Temperature; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics*
chemical_list: D005971:Glutamates; D005973:Glutamine; D018698:Glutamic Acid; D005696:Galactosidases; D001616:beta-Galactosidase