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J Biol Chem. 1990 Jul 5;265(19):10817-20.

Identification of an active-site residue in yeast invertase by affinity labeling and site-directed mutagenesis.

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  • 1Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany.

Abstract

Deglycosylated yeast invertase is irreversibly inactivated by conduritol B epoxide (CBE), an active-site-directed reagent. The inactivated enzyme contained 0.8 mol of CBE/mol of invertase monomer suggesting that the inactivation results from the modification of a single amino acid residue. Peptic digestion of [3H]CBE-labeled invertase followed by reverse phase column chromatography yielded two labeled peptides, both located at the amino-terminal end of the enzyme. Sequence analyses of these peptides revealed that Asp-23 is the modified residue. The role of Asp-23 in the catalytic process was investigated by changing it to Asn using site-directed mutagenesis of the SCU2 gene. The mutant enzyme was basically inactive, confirming a role for Asp-23 in the catalytic process.

PMID:
2113524
[PubMed - indexed for MEDLINE]
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