ROLE OF NOVEL DYE-LINKED DEHYDROGENASES IN THE METABOLISM OF POLYETHYLENE-GLYCOL BY PURE CULTURES OF SPHINGOMONAS SP N6

Polyethylene glycol and diglycolic acid dehydrogenase acitivities link ed with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide and phenazine methosulfate were found in the particulate fraction of t he sonic extract of a newly isolated polyethylene glycol 20 000-utiliz ing bacterium (Sphingomonas sp. N6). The amount of glyoxylic acid form ed from diglycolic acid increased proportionally with the increase in reaction time and enzyme concentration to show that diglycolic acid ca n be a model compound for an ether-cleaving enzyme. Both enzymes were formed inducibly when the organism was grown on polyethylene glycol 10 000. Both enzymes transferred many more electrons to 3-(4,5-dimethyl- 2-thiazolyl)-2,5-diphenyl tetrazolium bromide plus phenazine methosulf ate than to 2,6-dichlorophenolindophenol plus phenazine methosulfate. Also, ferricyanide, nitroblue tetrazolium and horse heart cytochrome c served as electron accepters, among which -dimethyl-2-thiazolyl)-2,5- diphenyl-2H-tetrazolium bromide plus phenazine methosulfate was most a ctive for polyethylene glycol dehydrogenase and ferricyanide was most active for diglycolic acid dehydrogenase irrespective of the presence of phenazine methosulfate. NAD and NADP did not act as electron accept ers. Polyethylene glycol dehydrogenase was completely inhibited by 1,4 -benzoquinone and partially inhibited by quinine and glyoxylic acid. D iglycolic acid dehydrogenase was strongly inhibited by 1,4-benzoquinon e and partially inhibited by alpha-benzoin oxime, quinacrine and glyox ylic acid. The enzymes appear to be different from each other and also from polyethylene glycol and diglycolic acid dehydrogenases of polyet hylene glycol 20 000-utilizing symbiotic mixed culture E-1 in which S. terrae was responsible for polyethylene glycol degradation in the cou pling with electron accepters and in the effect of inhibitors.