Mechanism‐based probes of the topology and function of fatty acid hydroxylases

The use of three mechanism‐based probes to investigate the topology and function of fatty acid hydroxylases is discussed. 1 ) The observation of protein rather than heme alkylation in the reaction of cytochrome P4504A1 with 10‐undecynoic acid supports the argument that the enzyme circumvents the inherent preference for ω ‐1 hydroxylation by restricting access to the ferryl oxygen. 2 ) The regiochemistry of the ferricyanide‐mediated iron‐to‐nitrogen shift of the cytochrome P450102 (P450 BM‐3 ) phenyl‐iron complex indicates that the active site of this bacterial fatty acid hydroxylase is open primarily above pyrrole ring A of the prosthetic heme group, 3 ) Inhibition of clofibrate‐mediated peroxisome proliferation in cultured rat hepatocytes by inactivation of cytochrome P4504A1 indicates that ω ‐hydroxylation of fatty acids provides a signal for peroxisome proliferation.—Ortiz de Montellano, P. R.; Chan, W. K.; Tuck, S. F.; Kaikaus, R. M.; Bass, N. M.; Peterson, J. A. Mechanism‐based probes of the topology and function of fatty acid hydroxylases. FASEB J. 6: 695‐699; 1992.