A non-conventional dissimilation pathway for long chain n-alkanes in Acinetobacter sp. M-1 that starts with a dioxygenase reaction

n-Alkane oxidation in a long chain n-alkane utilizer, Acinetobacter sp. M- l, was investigated. In Acinetobacter, n-alkanes have been postulated to be converted to the acid via a non-conventional oxidation pathway: n-alkane → n-alkyl hydroperoxide → aldehyde → acid (Finnerty, W.R.: Lipids of Acinetobacter. In Proceedings of the World Conference on Biotechnology for the Fats and Oils Industry, 184-188, 1988). However, there is little biochemical information on the enzymes involved in the postulated pathway, particularly the enzyme catalyzing the first step. In this study, we purified an n-alkane-oxidizing enzyme to apparent homogeneity by SDS-PAGE. The enzyme was a flavoprotein, and required molecular oxygen and Cu²⁺ for its activity, but did not require a reduced coenzyme such as NAD(P)H. A hydroperoxide was detected as a product of the enzyme reaction. We assume that the n-alkane-oxidizing enzyme is a dioxygenase. In addition, as a fatty alcohol does not appear to be an intermediate, fatty alcohol dehydrogenase is assumed not to participate in the n-alkane oxidation. The validity of the postulated pathway is supported by the following observations: (i) n-alkane monooxygenase activity was not detected, (ii) fatty alcohol dehydrogenase activities were low, and (iii) NAD(P)H-dependent long chain fatty aldehyde dehydrogenase activities were strongly induced in n-alkane-grown cells. NAD(P)H-dependent fatty aldehyde reductase activity was also found in n- alkane-grown cells, which may contribute to the formation of waxes that are cell reserve substances in n-alkane-utilizing Acinetobacter.