Reaction of the anionic acetylation agent methyl acetyl phosphate with D-3-hydroxybutyrate dehydrogenase.
Methyl acetyl phosphate is a competitive inhibitor of the reduction of acetoacetate by D-3-hydroxybutyrate dehydrogenase. The material also irreversibly inactivates the enzyme. The kinetics of the inactivation are consistent with methyl acetyl phosphate acetylating the conjugate base of a hydrogen bond donor. Protection offered by a substrate analogue (methyl acetonylphosphonate) in the presence of coenzyme implicates reaction at the cationic active site. Reversible protection by the amino group reagent 2,3-dimethylmaleic anhydride suggests that methyl acetyl phosphate reacts with an amino group. Sulfhydryl reagents and acetyl phosphate, a poorer acetylating agent, do not inactivate the enzyme. The pH dependence of the inactivation suggests that the acetylation occurs at a site that has a pKa of 8.2. The utility of methyl acetyl phosphate and other acyl phosphate monoesters in reacting with lysines adjacent to cationic sites of enzymes, hemoglobin, and histones is noted.
D006884:Hydroxybutyrate Dehydrogenase / Q000037:antagonists & inhibitors*; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D011549:Pseudomonas / Q000201:enzymology
D009943:Organophosphorus Compounds; D009243:NAD; C014660:methylacetylphosphonate; D006884:Hydroxybutyrate Dehydrogenase; D010746:Phosphonoacetic Acid