Methanol and Ethanol Oxidase Respiratory Chains of the Methylotrophic Acetic Acid Bacterium, Acetobacter methanolicus1

Publisher Website
Google Scholar
Abstract
Acetobacter methanolicus is a unique acetic acid bacterium which has a methanol oxidase respiratory chain, as seen In methylotrophs, in addition to Its ethanol oxidase respiratory chain. In this study, the relationship between methanol and ethanol oxidase respiratory chains was investigated. The organism Is able to grow by oxidizing several carbon sources, Including methanol, glycerol, and glucose. Cells grown on methanol exhibited a high methanol-oxidizing activity and contained large amounts of methanol dehydrogenase and soluble cytochromes c. Cells grown on glycerol showed higher oxygen uptake rate and dehydrogenase activity with ethanol but little methanol-oxidizing activity. Furthermore, two different terminal oxidases, cytochrome c and ubiqulnol oxidases, have been shown to he involved in the respiratory chain; cytochrome c oxidase predominates in cells grown on methanol while ubiqulnol oxidase predominates in cells grown on glycerol. Both terminal oxidases could be solubilized from the membranes and separated from each other. The cytochrome c oxidase and the ubiquinol oxidase have been shown to be a cytochrome co and a cytochrome bo, respectively. Methanol-oxidLzing activity was diminished by several treatments that disrupt the integrity of the cells. The activity of the Intact cells was inhibited with NaC1 and/or EDTA, which disturbed the interaction between methanol dehydrogenase and cytochrome c. Ethanol-oxidizing activity In the membranes was inhibited with 2-heptyl-4-hydroxyquinollne N-oxide, which inhibited ubiqulnol oxidase but not cytochrome c oxidase. Alcohol dehydrogenase has been purified from the membranes of glycerol-grown cells and shown to reduce ubiqulnone-lO as well as a short side-chain homologue in detergent solution. Furthermore, the ethanol oxldase respiratory chain was reconstituted into proteoliposomes containing alcohol dehydrogenase together with ubiquinone-lO and cytochrome ho. Thus, the results obtained in this study suggest that A. methanolicus has two independent respiratory chains for methanol and ethanol. The methanol oxidase respiratory chain appears to operate by linking methanol dehydrogenase to cytochrome c oxldase, cytochrome co, via soluble cytochrome(s) c, while the ethanol oxidase respiratory chain consists of alcohol dehydrogenase, ublquinone, and cytochrome bo ubiquinol oxidase.

This publication has 0 references indexed in Scilit: