Abstract
A steady-state kinetic analysis with evaluation of product inhibition was accomplished with purified rat liver flavokinase and FAD synthetase. For flavokinase, K m values were calculated as approximately 11 μ m for riboflavin and 3.7 μ m for ATP. K i values were calculated for FMN as 6 μ m against riboflavin and for ZnADP as 120 μ m against riboflavin and 23 μ m against ZnATP. From the inhibition pattern, the flavokinase reaction followed an ordered bi bi mechanism in which riboflavin binds first followed by ATP; ADP is released first followed by FMN. For FAD synthetase, K m values were calculated as 9.1 μ m for FMN and 71 μ m for MgATP. K i values were calculated for FAD as 0.75 μ m against FMN and 1.3 μ m against MgATP and for pyrophosphate as 66 μ m against FMN. The product inhibition pattern suggests the FAD synthetase reaction also followed an ordered bi bi mechanism in which ATP binds to enzyme prior to FMN, and pyrophosphate is released from enzyme before FAD. Comparison of K i values with physiological concentrations of FMN and FAD suggests that the biosynthesis of FAD is most likely regulated by this coenzyme as product at the stage of the FAD synthetase reaction.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
