title: 2-octynoyl coenzyme A is a mechanism-based inhibitor of pig kidney medium-chain acyl coenzyme A dehydrogenase: isolation of the target peptide.
abstract: Pig kidney medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) is irreversibly and stoichiometrically inactivated by [1-14C]-2-octynoyl coenzyme A. The linkage is stable at pH 2-6, but labile under basic conditions. The inhibitor labels a unique tryptic peptide, Ile-Tyr-Gln-Ile-Tyr-Glu-Gly-Thr-Ala-Gln-Ile-Gln-Arg, close to the C-terminus of the protein. The peptide is labeled at Glu-401 with the acyl moiety of the inhibitor but does not contain detectable coenzyme A. Both the inactivation of the dehydrogenase and the appearance of an absorption band at 800 nm show large primary deuterium isotope effects using 4,4'-dideuterio-2-octynoyl-CoA (7.3 and 6.3, respectively). Thus, 2-octynoyl-CoA is a mechanism-based inactivator of the dehydrogenase and is activated by rate-limiting gamma-proton abstraction. Glutamate-401 may be the base that abstracts the pro-R alpha-proton during the dehydrogenation of normal substrates.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark 19716.
authors.forename: P J
authors.initials: PJ
authors.lastname: Powell
authors.forename: C
authors.initials: C
authors.lastname: Thorpe
mesh_terms: D000214:Acyl Coenzyme A / Q000138:chemical synthesis / Q000494:pharmacology*; D042964:Acyl-CoA Dehydrogenase; D044944:Acyl-CoA Dehydrogenases / Q000037:antagonists & inhibitors*; D000595:Amino Acid Sequence; D000818:Animals; D007202:Indicators and Reagents; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D011485:Protein Binding; D013053:Spectrophotometry; D013552:Swine
chemical_list: D000214:Acyl Coenzyme A; D007202:Indicators and Reagents; C058947:2-octynoyl-coenzyme A; D044944:Acyl-CoA Dehydrogenases; D042964:Acyl-CoA Dehydrogenase