An improved assay for pyruvate dehydrogenase in liver and heart.
A radiochemical assay was developed to measure pyruvate dehydrogenase complex (PDC) activity in liver and heart without interference by branched-chain 2-oxo acid dehydrogenase (BCODH). Decarboxylation of pyruvate by BCODH was eliminated by using low pyruvate concentration (0.5 mM), a preferred substrate for BCODH (3-methyl-2-oxopentanoate) that is not used by PDC, and a competitive inhibitor of BCODH, dichloroacetate. This method was validated by assaying a combination of both purified enzymes and tissue homogenates with known amounts of added BCODH. The actual percentage of active PDC decreased after 48 h starvation from 13.6 to 3.1 in liver and from 77.1 to 9.0 in heart. Total PDC activity (munits of PDC/units of citrate synthase) in starved rats was increased by 34% in liver and decreased by 23% in heart. Total PDC activity (munits/g wet wt.) in fed- and starved-rat liver was 0.8 and 1.3, and in heart was 6.6 and 5.8, respectively.
Paxton
R
R
Department of Physiology and Pharmacology, Auburn University, AL 36849-5520.
Sievert
L M
LM
D000818:Animals; D002250:Carbon Radioisotopes; D004435:Eating; D007202:Indicators and Reagents; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D011768:Pyruvate Dehydrogenase Complex / Q000032:analysis* / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D011865:Radioisotope Dilution Technique; D051381:Rats; D013217:Starvation
D002250:Carbon Radioisotopes; D007202:Indicators and Reagents; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates