Open Accesskinetic Studies on the Reaction Mechanism and the Citrate Activation or Liver Acetyl Coenzyme A Carboxylase
Author(s) -
Hashimoto Tkashi,
Numa Shosaku
Publication year - 1971
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1971.tb01247.x
Subject(s) - chemistry , pyruvate carboxylase , enzyme , reversible reaction , coenzyme a , cofactor , product inhibition , acetyl coa , reaction mechanism , biochemistry , citrate synthase , catalysis , acetyl coa carboxylase , active site , stereochemistry , non competitive inhibition , reductase
Kinetoc studies were carried out on the reaction mechanism of rat liver acetyl coenzyme A carboxylase. The results of initial velocity and product inhibition studies on the forward and reverse reaction indicate that the carboxylase reaction is most likely to proceed through the “bi bi uni uni ping pong” mechanism. The order of the addition of substrates to the enzyme is as follos: ATP, HCO 3 ‐ and acetyl‐CoA in the forward reaction, and malonyl‐CoA, P i and ADP in the reverse reaction. Kinetic analysis of the stimulatory effect of citrate on the initial velocities of the forward and reverse reaction indicate that the site of citrate action during catalysis lies predominantly onthe earboxylated enzyme. It is proposed that there exists and equilibrium between active and inactive forms of the carboxybiotinyl enzyme and that this equilibrium is shifted toward the active form in the presence of citrate.