The "super mutant" of yeast FMN adenylyltransferase enhances the enzyme turnover rate by attenuating product inhibition.

Carlos Huerta, Nick V Grishin, Hong Zhang

Biochemistry 2013 May 28

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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.

Citation

Carlos Huerta, Nick V Grishin, Hong Zhang. The "super mutant" of yeast FMN adenylyltransferase enhances the enzyme turnover rate by attenuating product inhibition. Biochemistry. 2013 May 28;52(21):3615-7