Pantothenic acid (vitamin B5 ) is the substrate for the biosynthesis of coenzyme A, an essential cofactor in energy metabolism. Because mammals obtain vitamin B5 from their diet, the biosynthesis of pantothenic acid in pathogenic bacteria has been identified as a drug target. Ketopantoate reductase (KPR) catalyzes the NADPH-dependent reduction of ketopantoate (KP) to pantoate, the essential precursor of pantothenic acid. Previous structural and kinetic studies have focused on Escherichia coli KPR, a monomeric enzyme with globular N- and C-terminal domains. The N terminal domain of E. coli KPR contains a Rossmann fold for binding NADPH. KP binds in the active site that is formed in the interface between the domains. The catalytic reaction follows a sequential ordered bi-bi kinetic mechanism in which the enzyme binds NADPH first, followed by KP for the hydride transfer. Here we report the structural and kinetic analysis of KPR from Staphylococcus aureus, an important human pathogen. Unlike the E. coli enzyme, S. aureus KPR forms a stable, dimeric complex that is highly conserved among several deeply divergent KPRs. Steady state analysis of the S. aureus enzyme also displays positive cooperativity with respect to the cofactor. We present evidence that the cooperativity is best explained by a random addition mechanism with a kinetically preferred path. Thus, the mechanism of S. aureus KPR is distinct from those of previously described members of the family of 2-hydroxyacid dehydrogenases.
(I always have trouble reading and comprehending scientific articles) What's the motivation for the investigation? How is the author's motivation for performing the investigation related to other work in the field?
Pantothenic acid (vitamin B5 ) is the substrate for the biosynthesis of coenzyme A, an essential cofactor in energy metabolism. Because mammals obtain vitamin B5 from their diet, the biosynthesis of pantothenic acid in pathogenic bacteria has been identified as a drug target. Ketopantoate reductase (KPR) catalyzes the NADPH-dependent reduction of ketopantoate (KP) to pantoate, the essential precursor of pantothenic acid. Previous structural and kinetic studies have focused on Escherichia coli KPR, a monomeric enzyme with globular N- and C-terminal domains. The N terminal domain of E. coli KPR contains a Rossmann fold for binding NADPH. KP binds in the active site that is formed in the interface between the domains. The catalytic reaction follows a sequential ordered bi-bi kinetic mechanism in which the enzyme binds NADPH first, followed by KP for the hydride transfer. Here we report the structural and kinetic analysis of KPR from Staphylococcus aureus, an important human pathogen. Unlike the E. coli enzyme, S. aureus KPR forms a stable, dimeric complex that is highly conserved among several deeply divergent KPRs. Steady state analysis of the S. aureus enzyme also displays positive cooperativity with respect to the cofactor. We present evidence that the cooperativity is best explained by a random addition mechanism with a kinetically preferred path. Thus, the mechanism of S. aureus KPR is distinct from those of previously described members of the family of 2-hydroxyacid dehydrogenases.
(I always have trouble reading and comprehending scientific articles) What's the motivation for the investigation? How is the author's motivation for performing the investigation related to other work in the field?
