In vivo inactivation of glycerol dehydrogenase in Klebsiella aerogenes: properties of active and inactivated proteins

Abstract

Glycerol:NAD+ 2-oxidoreductase (EC 1.1.1.6), an inducible enzyme for anaerobic glycerol catabolism in K. aerogenes [pneumoniae], was purified and had a MW of 79,000 by gel electrophoresis. The protein seemed to be enzymatically active either as a dimer of a 40,000-dalton peptide at pH 8.6 or as a tetramer of 160,000 MW at pH 7.0. The enzyme activity was present at high levels in cells growing anaerobically on glycerol, but disappeared with a half-life of about 45 min if O2 was introduced to the culture. In contrast, no such phenomenon occurred with dihydroxyacetone kinase activity, the 2nd enzyme in the pathway. Immunochemical analysis showed that the inactivation of the oxidoreductase did not involve degradation of the protein. Subunits of the active and inactive forms of the enzyme were indistinguishable in size on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and had similar isoelectric points (pH 4.7). Inactivation did, alter the gel filtration properties of the enzyme protein and, more importantly, reduced its affinity for the dye Cibacron F3GA and the coenzyme NAD+.