乙酰辅酶A羧化酶
丙酮酸羧化酶
生物素
生物化学
脂肪酸合成
乙酰辅酶A
酶
羧化
大肠杆菌
生物
化学
基因
催化作用
作者
T.C. Broussard,Amanda E. Price,Susan M. Laborde,Grover L. Waldrop
出处
期刊:Biochemistry
[American Chemical Society]
日期:2013-04-17
卷期号:52 (19): 3346-3357
被引量:42
摘要
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.
科研通智能强力驱动
Strongly Powered by AbleSci AI