Pyruvate dehydrogenase and 3-fluoropyruvate: chemical competence of 2-acetylthiamin pyrophosphate as an acetyl group donor to dihydrolipoamide.
The pyruvate dehydrogenase component (E1) of the pyruvate dehydrogenase complex catalyzes the decomposition of 3-fluoropyruvate to CO2, fluoride anion, and acetate. Acetylthiamin pyrophosphate (acetyl-TPP) is an intermediate in this reaction. Incubation of the pyruvate dehydrogenase complex with 3-fluoro[1,2-14C]pyruvate, TPP, coenzyme A (CoASH), and either NADH or pyruvate as reducing systems leads to the formation of [14C]acetyl-CoA. In this reaction the acetyl group of acetyl-TPP is partitioned by transfer to both CoASH (87 +/- 2%) and water (13 +/- 2%). When the E1 component is incubated with 3-fluoro[1,2-14C]pyruvate, TPP, and dihydrolipoamide, [14C]acetyldihydrolipoamide is produced. The formation of [14C]acetyldihydrolipoamide was examined as a function of dihydrolipoamide concentration (0.25-16 mM). A plot of the extent of acetyl group partitioning to dihydrolipoamide as a function of 1/[dihydrolipoamide] showed 95 +/- 2% acetyl group transfer to dihydrolipoamide when dihydrolipoamide concentration was extrapolated to infinity. It is concluded that acetyl-TPP is chemically competent as an intermediate for the pyruvate dehydrogenase complex catalyzed oxidative decarboxylation of pyruvate.
D002250:Carbon Radioisotopes; D007700:Kinetics; D011485:Protein Binding; D030481:Pyruvate Dehydrogenase (Lipoamide); D011768:Pyruvate Dehydrogenase Complex / Q000302:isolation & purification / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism*; D013835:Thiamine Pyrophosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D008063:Thioctic Acid / Q000031:analogs & derivatives* / Q000378:metabolism
D002250:Carbon Radioisotopes; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates; C017319:3-fluoropyruvate; C051074:2-acetylthiamine pyrophosphate; C007409:dihydrolipoamide; D008063:Thioctic Acid; D030481:Pyruvate Dehydrogenase (Lipoamide); D013835:Thiamine Pyrophosphate