Regulation of enzymes by fatty acyl coenzyme A. Interactions of short and long chain spin-labeled acyl-CoA with the acetyl-CoA site on pig heart citrate synthase.

摘要: The binding of two similar spin-labeled fatty acyl-CoA analogues, one short chain, 6-doxyloctanoyl-CoA (S-(2-(5-carboxybutyl)-2-ethyl-4, 4-dimethyl-3-oxazolidinyl-N-oxyl)-CoA) and long 6-doxylstearoyl-CoA (S-(2-(5-carboxybutyl)-2-dodecyl-4, to pig heart citrate synthase (citrate oxaloacetate-lyase (pro-3S-CH2COO- leads acetyl-CoA) EC 4.1.3.7) has been compared. the chain analogue could be satisfactorily fit by a classical treatment (independent, noninteracting sites) with well defined stoichiometry: 2 mol spin label bound per dimeric enzyme. Binding was complex in excess mol/dimer. Competitive experiments using either presence various nucleotides substrates revealed differences analogues. These additional studies, together kinetic measurements, implied isosteric acyl-CoA, ATP, NADPH, NADH, NADP+, acetyl-CoA, partial acyl-CoA. NADPH NADP+ same form enzyme, perhaps through overlapping sites, kinetically verified even though these had differing effects on Oxalacetate shown decrease but have no effect chain. This result supported measurements. competitive suggested that its isotherm resulted from classes i.e. cooperative nucleotide sites other sites. An empirical mathematical model employing this rationale provided satisfactory for synthase. A acid which not native enzyme appreciably palmitoyl-CoA. might identified sets proposed model. previous results were correlated properties CoA site crystallographically (Remington, S., Wiegand, G., Huber, R. (1982) J. Mol. Biol. 158, 111-152).