Diversity of dioxygenases that catalyze the first step of oxidation of long-chainn-alkanes inAcinetobactersp. M-1

Abstract

Three kinds of enzymes, designated A, B and C, involved in n-alkane oxidation were found in the cytoplasm of n-alkanegrownAcinetobacter sp. M-1. All catalyzed the dioxygenation of n-alkanes to the corresponding n-alkyl hydroperoxides. Purified enzyme A consisted of four identical subunits having a molecular mass of 72 kDa. The enzyme was strongly inhibited by several iron-chelating agents, such as o-phenanthroline, 8-hydroxyquinoline and α,α′-dipyridyl, and could be distinguished from enzyme C, a Cu2+-requiring flavoprotein. Enzyme B was relatively unstable on purification. The three enzymes used n-alkanes, n-alkenes, and aryl compounds with longer alkyl side chains as substrates. Enzymes B and C were more active toward relatively short n-alkanes (C12–16). Enzyme A oxidized solid n-alkanes well, the most preferable substrate being tetracosane (C24). Enzyme A is responsible for about 80% of the total activity found in the soluble fraction of n-alkane-grown Acinetobacter sp. M-1, indicating that the enzyme plays a major role during growth on solid n-alkanes.