Cytochrome P-450cam and Other Bacterial P-450 Enzymes

Abstract

The purpose of this chapter is twofold. First, we will attempt to summarize the existing knowledge on the wide variety of bacterial cytochrome P-450 hemeproteins that have been discovered. As such, this represents the first comprehensive review of the bacterial cytochromes P-450. It should become evident to the reader that these cytochromes comprise a class just as diverse, if not more so, than their eukaryotic counterparts. Perhaps the best known and most extensively characterized of these bacterial enzymes is P-450cam isolated from Pseudomonas putida. From the initial isolation in Gunsalus’s laboratory in 1967 and subsequent investigations in many laboratories, the numerous studies employing this cytochrome have shed much light on the mechanisms associated with the family of P-450-dependent monooxygenases as a whole. A second goal of this chapter is to review the detailed biophysical, biochemical, and molecular biological studies conducted with this system. It should be noted that “P-450cam” and “bacterial P-450” are not synonymous. The various P-450 molecules described herein are in all probability only a very small fraction of those present in the myriad of bacterial cells in the biosphere. In view of the variety of substrate transformations that this enzyme family is able to catalyze, some of which are energetically very difficult, their distribution in nature is no doubt ubiquitous. One need only look through the American Type Culture Collection Catalogue1 under such diverse genera as Pseudomonas, Rhodococcus, Bacillus, and Nocardia among others to see the potential roles of yet undiscovered P-450 monooxygenases in the degradation and transformation of a plethora of compounds. Even if only a small portion of the enzymes involved in these various biotransformations are P-450 isozymes, there would correspond many hundreds of P-450 hemeproteins with definable specificities.