title: The "super mutant" of yeast FMN adenylyltransferase enhances the enzyme turnover rate by attenuating product inhibition.
abstract: FMN adenylyltransferase (FMNAT) is an essential enzyme catalyzing the last step of a two-step pathway converting riboflavin (vitamin B2) to FAD, the ubiquitous flavocoenzyme. A structure-based mutagenesis and steady-state kinetic analysis of yeast FMNAT unexpectedly revealed that mutant D181A had a much faster turnover rate than the wild-type enzyme. Product inhibition analysis showed that wild-type FMNAT is strongly inhibited by FAD, whereas the D181A mutant has an attenuated product inhibition. These results provide a structural basis for the product inhibition of the enzyme and suggest that product release may be the rate-limiting step of the reaction.
authors.affiliation: Department of Biophysics and Department of Biochemistry and ‡Howard Hughes Medical Institute, University of Texas Southwestern Medical Center , 5323 Harry Hines Boulevard, Dallas, Texas 75390, United States.
authors.forename: Carlos
authors.initials: C
authors.lastname: Huerta
authors.forename: Nick V
authors.initials: NV
authors.lastname: Grishin
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D055162:Biocatalysis; D005486:Flavin Mononucleotide / Q000037:antagonists & inhibitors / Q000378:metabolism; D007700:Kinetics; D016296:Mutagenesis; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
chemical_list: D005486:Flavin Mononucleotide; D009713:Nucleotidyltransferases; C020143:FMN adenylyltransferase