The pyruvate-dehydrogenase complex from Azotobacter vinelandii. 2. Regulation of the activity.
The presence of activators(AMP and sulphate) or inhibitors(acetyl-CoA) has no influence on the Hill coefficient of the S-shaped [pyruvate]--velocity curve of either the pyruvate-NAD+ overall reaction(h equals 2.5) or that of the pyruvate-K3Fe(CN)6 ACTIVITY OF THE FIRST ENZYME (H EQUALs 1.3). pH STUDIES INDICATED THAT THE Hill coefficient is dependent on subunit ionization within the pyruvate-containing complex and not on those in the free complex. It is concluded that pyruvate conversion rather that pyruvate binding is responsible for the allosteric pattern. The activity is due to absence of a protein kinase, mainly regulated at the acetyl-CoA/CoA, and NADH/NAD+ levels and by the value of the energy charge.
D000105:Acetyl Coenzyme A / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D001395:Azotobacter / Q000201:enzymology*; D004735:Energy Transfer; D004789:Enzyme Activation / Q000187:drug effects; D005292:Ferricyanides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008433:Mathematics; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D013431:Sulfates / Q000494:pharmacology; D013835:Thiamine Pyrophosphate / Q000494:pharmacology
D005292:Ferricyanides; D011768:Pyruvate Dehydrogenase Complex; D013431:Sulfates; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000105:Acetyl Coenzyme A; D008274:Magnesium; D013835:Thiamine Pyrophosphate