The Copper Ions in the Membrane-Associated Methane Monooxygenase

Abstract

The enzyme methane monooxygenase (MMO)1 in methanotrophic bacteria catalyzes the conversion of methane to methanol using molecular oxygen as co-substrate [1]. Two forms of MMO differing in cellular location are known to exist [2]. The soluble methane monooxygenase (sMMO) found in the cytosolic traction of the bacteria appears to be restricted to only Methylococcus and Methylosinus strains and is expressed only at limiting copper levels in the growth medium [3–5]. The particulate methane monooxygenase (pMMO) found in the membrane fraction of the cells appears to be expressed in all types of methanotrophic bacteria [3–6]. Only the sMMO has been purified and extensively characterized [7–11].