Comparison of the active sites of the purified carnitine acyltransferases from peroxisomes and mitochondria by using a reaction-intermediate analogue

A. N. Nic Bhaird, G. Kumaravel, T. R D Gandour, T. M J Krueger, R. R. Ramsay*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

The carnitine acyltransferases contribute to the modulation of the acyl-CoA/CoA ratio in various cell compartments with consequent effects on many aspects of fatty acid metabolism. The properties of the enzymes are different in each location. The kinetic mechanisms and kinetic parameters for the carnitine acyltransferases purified from peroxisomes (COT) and from the mitochondrial inner membrane (CPT-II) were determined. Product-inhibition studies established that COT follows a rapid-equilibrium random-order mechanism, but CPT-II follows a strictly ordered mechanism in which acyl-CoA or CoA must bind before the carnitine substrate. Hemipalmitoylcarnitinium [(+)HPC], a prototype tetrahedral intermediate analogue of the acyltransferase reaction, inhibits CPT-II 100-fold better than COT. ( +)-HPC behaves as an analogue of palmitoyl-L-carnitine with COT. In contrast, with CPT-II ( +)-HPC binds more tightly to the enzyme than do substrates or products, suggesting that it is a good model for the transition state and, unlike palmitoyl-L-carnitine, ( +)-HPC can bind to the free enzyme. The data support the concept of three binding domains for the acyltransferases, a CoA site, an acyl site and a carnitine site. The CoA site is similar in COT and CPT-II, but there are distinct differences between the carnitine-binding site which may dictate the kinetic mechanism.

Original languageEnglish
Pages (from-to)645-651
Number of pages7
JournalBiochemical Journal
Volume294
Issue number3
Publication statusPublished - 1 Jan 1993

Fingerprint

Dive into the research topics of 'Comparison of the active sites of the purified carnitine acyltransferases from peroxisomes and mitochondria by using a reaction-intermediate analogue'. Together they form a unique fingerprint.

Cite this