title: Effects of alpha-ketoisovalerate on bovine heart pyruvate dehydrogenase complex and pyruvate dehydrogenase kinase.
abstract: The regulatory effects of alpha-ketoisovalerate on purified bovine heart pyruvate dehydrogenase complex and endogenous pyruvate dehydrogenase kinase were investigated. Incubation of pyruvate dehydrogenase complex with 0.125 to 10 mM alpha-ketoisovalerate caused an initial lag in enzymatic activity, followed by a more linear but inhibited rate of NADH production. Incubation with 0.0125 or 0.05 mM alpha-ketoisovalerate caused pyruvate dehydrogenase inhibition, but did not cause the initial lag in pyruvate dehydrogenase activity. Gel electrophoresis and fluorography demonstrated the incorporation of acyl groups from alpha-keto[2-14C]isovalerate into the dihydrolipoyl transacetylase component of the enzyme complex. Acylation was prevented by pyruvate and by arsenite plus NADH. Endogenous pyruvate dehydrogenase kinase activity was stimulated specifically by K+, in contrast to previous reports, and kinase stimulation by K+ correlated with pyruvate dehydrogenase inactivation. Maximum kinase activity in the presence of K+ was inhibited 62% by 0.1 mM thiamin pyrophosphate, but was inhibited only 27% in the presence of 0.1 mM thiamin pyrophosphate and 0.1 mM alpha-ketoisovalerate. Pyruvate did not affect kinase inhibition by thiamin pyrophosphate at either 0.05 or 2 mM. The present study demonstrates that alpha-ketoisovalerate acylates heart pyruvate dehydrogenase complex and suggests that acylation prevents thiamin pyrophosphate-mediated kinase inhibition.
mesh_terms: D000818:Animals; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D045782:Hemiterpenes; D007651:Keto Acids / Q000494:pharmacology*; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D011189:Potassium Chloride / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D011773:Pyruvates / Q000494:pharmacology; D019289:Pyruvic Acid; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000494:pharmacology
chemical_list: D045782:Hemiterpenes; D007651:Keto Acids; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates; D011189:Potassium Chloride; C001505:alpha-ketoisovalerate; D019289:Pyruvic Acid; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D013835:Thiamine Pyrophosphate