Diversity of Alkane Hydroxylase Systems in the Environment

The first step in the aerobic degradation of alkanes by bacteria, yeasts, and fungi is catalyzed by oxygenases. These enzymes, which introduce oxygen atoms derived from molecular oxygen into the alkane substrate, play an important role in oil bioremediation and in the cometabolic degradation of compounds such as trichloroethylene and fuel oxygenates. In addition, they are useful biocatalysts and important models for a difficult chemical reaction: the regio- and stereospecific activation of C-H bonds. Several unrelated enzyme classes catalyze the oxidation of alkanes. Alkane-degrading yeast strains contain multiple alkane hydroxylases belonging to the P450 superfamily, while many bacteria contain enzymes related to the Pseudomonas putida GPo1 membrane-bound alkane hydroxylase system. Short-chain alkanes are probably oxidized by alkane hydroxylases related to the soluble and particulate methane monooxygenases. Only the membrane-bound enzymes have been studied with respect to their prevalence in environments such as soils or aquifers.