Fermentation of 1,2-Propanediol and 1,2-Ethanediol by Some Genera of Enterobacteriaceae , Involving Coenzyme B ₁₂ -Dependent Diol Dehydratase

Abstract

Klebsiella pneumoniae (Aerobacter aerogenes) ATCC 8724 was able to grow anaerobically on 1,2-propanediol and 1,2-ethanediol as carbon and energy sources. Whole cells of the bacterium grown anaerobically on 1,2-propanediol or on glycerol catalyzed conversion of 1,2-diols and aldehydes to the corresponding acids and alcohols. Glucose-grown cells also converted aldehydes, but not 1,2diols, to acids and alcohols. The presence of activities of coenzyme B12-dependent diol dehydratase, alcohol dehydrogenase, coenzyme-A-dependent aldehyde dehydrogenase, phosphotransacetylase, and acetate kinase was demonstrated with crude extracts of 1,2-propanediol-grown cells. The dependence of the levels of these enzymes on growth substrates, together with cofactor requirements in in vitro conversion of these substrates, indicates that 1,2-diols are fermented to the corresponding acids and alcohols via aldehydes, acyl-coenzyme A, and acyl phosphates. This metabolic pathway for 1,2-diol fermentation was also suggested in some other genera ofEnterobacteriaceae which were able to grow anaerobically on 1,2-propanediol. When the bacteria were cultivated in a 1,2-propanediol medium not supplemented with cobalt ion, the coenzyme B12-dependent conversion of 1,2-diols to aldehydes was the rate-limiting step in this fermentation. This was because the intracellular concentration of coenzyme B12 was very low in the cells grown in cobalt-deficient medium, since the apoprotein of diol dehydratase was markedly induced in the cells grown in the 1,2-propanediol medium. Better cell yields were obtained when the bacteria were grown anaerobically on 1,2propanediol. Evidence is presented that aerobically grown cells have a different metabolic pathway for utilizing 1,2-propanediol.

Purification, characterization and subunits identification of the diol dehydratase of Lactobacillus collinoides

“…Cyanocobalamin (CNCbl) is a competitive inhibitor of diol and glycerol dehydratases and its effect on the enzyme of L. collinoides was studied. Figure 5B For all the dehydratases characterized [2][3][4][5][6][7], monovalent cations seem to be required for the catalytic activity. The influence of various mono and divalent cations in low concentrations (10 mM) on the diol dehydratase activity was then studied (data not shown).…”

Biochemistry of coenzyme B12-dependent glycerol and diol dehydratases and organization of the encoding genes

“…This enzyme seems to be entirely di¡erent from the B IP -containing dehydratases and will not be discussed here any further. In the case of enteric bacteria, B IP -dependent glycerol or diol dehydratases were detected in some strains of the genera Salmonella, Klebsiella, Enterobacter and Citrobacter [7,15,18,22,23,25,29]. Both dehydratases may occur individually or together in these organisms.…”

“…Diol dehydratase is used by some enteric and propionic acid bacteria for the degradation of 1,2-propanediol [7,22]. Catabolism of this small molecule is likely to be important in a variety of nutritionally complex environments.…”

“…Coenzyme A-dependent aldehyde dehydrogenase, phosphotransacylase, propionate kinase, and alcohol dehydrogenase are proposed to catalyze this disproportionation ( Fig. 2A) [7,8]. Fermentation of 1,2propanediol provides one ATP per molecule of propanediol, but no source of carbon.…”

Molecular basis for specificities of reactivating factors for adenosylcobalamin‐dependent diol and glycerol dehydratases

“…These enzymes encoded in the pdu (propanediol utilization) operon [6–8] and the dha (dihydroxyacetone) regulon [9–12], respectively, are involved in producing the electron acceptors propionaldehyde and β‐hydroxypropionaldehyde. They are essential for the fermentation of 1,2‐propanediol and glycerol, respectively [4,13–17] because these carbon sources are more reduced substrates than the corresponding carbohydrates, and oxidation and reduction must be balanced for the bacterial growth under anaerobic conditions. In some bacteria, glycerol dehydratase can be substituted by the isofunctional diol dehydratase, which is induced at a low level by glycerol [9,14,18].…”