The Methanol-Oxidizing System of Methylobacterium extorquens AM1 Reconstituted with Purified Constituents

抄録

The electron transport system (with cytochrome aa₃) coupled to the oxidation of methanol in Methylobacterium extorquens AM1 (former Pseudomonas AM1) was reconstituted with highly purified constituents of the system. A mixture of 2.7μM methanol dehydrogenase, 3.2μM cytochrome cH, and 71nM cytochrome c oxidase (=cytochrome aa₃) consumed oxygen at a lower rate in the presence of methanol, while its activity was enhanced 3-fold by the addition of 1.4μM cytochrome cL (74 mol of O₂ consumed/mol of heme a of cytochrome c oxidase per min). Further addition of amicyanin to the above mixture did not affect the activity. Although ammonium ion greatly activated the activity of methanol dehydrogenase, the ion had little effect on the oxygen consumption activity of the above mixture. On the basis of the results obtained in the present study, an electron transport system is proposed for the oxidation of methanol in M. extorquens AM1.