[Interaction of thiamine pyrophosphate and some of its analogs with the pyruvate dehydrogenase complex from the adrenal cortex].
Highly purified preparations of the pyruvate dehydrogenase complex from bovine adrenals partially contain strongly bound thiamine pyrophosphate (TPP) which provides to 35% of the maximal activity measured under saturation with the exogenous TPP. The dependence of the complex-catalyzed reaction rate on the TPP concentration is described by Michaelis-Menten equation. The apparent value of Km for TPP without Mg2+ is 2.3 mumol. Magnesium ions reduce Km to 1.1 mumol. The constant of the TPP with the enzyme association rate calculated by the lag-period without Mg2+ is 3043 mol-1 s-1 in the presence of Mg2+ it is 9090 mol-1 . s-1. Phosphorus ethers of oxy- and tetrahydrothiamine produce a competitive type inhibition on the pyruvate dehydrogenase complex with respect to TPP. Oxythiamine pyrophosphate (Ki--0,07 microM) and tetrahydrothiamine pyrophosphate (Ki--0,1 microM) possess the highest inhibitory action.
D000302:Adrenal Cortex / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013835:Thiamine Pyrophosphate / Q000031:analogs & derivatives / Q000494:pharmacology*
D011768:Pyruvate Dehydrogenase Complex; D008274:Magnesium; D013835:Thiamine Pyrophosphate
Vsaimodeĭstvie tiaminpirofosfata i nekotorykh ego analogov s piruvatdegidrogenaznym kompleksom kory nadpochechnikov.