Title
Complex formation and regulation of Escherichia coli acetyl-CoA carboxylase
Document Type
Article
Publication Date
5-14-2013
Abstract
Acetyl-CoA carboxylase is a biotin-dependent enzyme that catalyzes the regulated step in fatty acid synthesis. The bacterial form has three separate components: biotin carboxylase, biotin carboxyl carrier protein (BCCP), and carboxyltransferase. Catalysis by acetyl-CoA carboxylase proceeds via two half-reactions. In the first half-reaction, biotin carboxylase catalyzes the ATP-dependent carboxylation of biotin, which is covalently attached to BCCP, to form carboxybiotin. In the second half-reaction, carboxyltransferase transfers the carboxyl group from carboxybiotin to acetyl-CoA to form malonyl-CoA. All biotin-dependent carboxylases are proposed to have a two-site ping-pong mechanism in which the carboxylase and transferase activities are separate and do not interact. This posits two hypotheses: either biotin carboxylase and BCCP undergo the first half-reaction, BCCP dissociates, and then BCCP binds to carboxyltransferase, or all three constituents form an enzyme complex. To determine which hypothesis is correct, a steady-state enzyme kinetic analysis of Escherichia coli acetyl-CoA carboxylase was conducted. The results indicated the two active sites of acetyl-CoA carboxylase interact. Both in vitro and in vivo pull-down assays demonstrated that the three components of E. coli acetyl-CoA carboxylase form a multimeric complex and that complex formation is unaffected by acetyl-CoA, AMPPNP, and mRNA encoding carboxyltransferase. The implications of these findings for the regulation of acetyl-CoA carboxylase and fatty acid biosynthesis are discussed.
Publication Source (Journal or Book title)
Biochemistry
First Page
3346
Last Page
57
Recommended Citation
Broussard, T. C., Price, A. E., Laborde, S. M., & Waldrop, G. L. (2013). Complex formation and regulation of Escherichia coli acetyl-CoA carboxylase. Biochemistry, 52 (19), 3346-57. https://doi.org/10.1021/bi4000707
