Enzymes Involved in Anaerobic Polyethylene Glycol Degradation by Pelobacter venetianus and Bacteroides Strain PG1

摘要

In extracts of polyethylene glycol (PEG)-grown cells of the strictly anaerobically fermenting bacterium Pelobacter venetianus, two different enzyme activities were detected, a diol dehydratase and a PEG-degrading enzyme which was characterized as a PEG acetaldehyde lyase. Both enzymes were oxygen sensitive and depended on a reductant, such as titanium citrate or sulfhydryl compounds, for optimal activity. The diol dehydratase was inhibited by various corrinoids (adenosylcobalamin, cyanocobalamin, hydroxocobalamin, and methylcobalamin) by up to 37% at a concentration of 100 μM. Changes in ionic strength and the K+ ion concentration had only limited effects on this enzyme activity; glycerol inhibited the enzyme by 95%. The PEG-degrading enzyme activity was stimulated by the same corrinoids by up to 80%, exhibited optimal activity in 0.75 M potassium phosphate buffer or in the presence of 4 M KCI, and was only slightly affected by glycerol. Both enzymes were located in the cytoplasmic space. Also, another PEG-degrading bacterium, Bacteroides strain PG1, contained a PEG acetaldehyde lyase activity analogous to the corresponding enzyme of P. venetianus but no diol dehydratase. Our results confirm that corrinoid-influenced PEG degradation analogous to a diol dehydratase reaction is a common strategy among several different strictly anaerobic PEG-degrading bacteria.