title: Site-directed mutagenesis of beta-galactosidase (E. coli) reveals that tyr-503 is essential for activity.
abstract: By using the technique of site-directed mutagenesis we have succeeded in replacing tyr-503 of beta-galactosidase (E. coli) with a phe. A study of the kinetic and stability properties of this mutant enzyme (F-503 beta-galactosidase) showed that the loss in activity upon this change is due to the loss of a catalytic group (rather than a detrimental change in the enzyme's overall structure or a change in the enzyme's binding capacity). This confirms previous suggestions that this tyr residue is involved in catalysis.
mesh_terms: D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics*; D005696:Galactosidases / Q000235:genetics*; D006358:Hot Temperature; D007700:Kinetics; D013329:Structure-Activity Relationship; D014443:Tyrosine; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D014443:Tyrosine; D005696:Galactosidases; D001616:beta-Galactosidase