Interactions of lipoyl domains with the E1p subunits of the pyruvate dehydrogenase multienzyme complex from Escherichia coli.
Equilibrium binding experiments were carried out with lipoyl domains and the pyruvate decarboxylase [pyruvate dehydrogenase (lipoamide), E1p, EC 1.2.4.1)] component of the pyruvate dehydrogenase multienzyme complex of Escherichia coli. The dissociation constant (Ks) was estimated to be not less than 0.3 mM, exceeding the Km value (33 microM) for reductive acetylation of the domains by an order of magnitude. Thus, the lipoyl domain, which is required to promote reductive acetylation of the lipoyl group, does not appear to do this simply by enhancing the binding to E1p. The difference between Ks and Km suggests that the formation and release of reductively acetylated lipoyl domains from the enzyme may be a relatively rapid step in the mechanism.
Department of Biochemistry, University of Cambridge, England.
L D
LD
Graham
R N
RN
Perham
D004926:Escherichia coli / Q000201:enzymology*; D011487:Protein Conformation; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000378:metabolism* / Q000031:analogs & derivatives
D011768:Pyruvate Dehydrogenase Complex; C033041:thiamine thiothiazolone pyrophosphate; D013835:Thiamine Pyrophosphate