Abstract
Glycerol:NAD+2-OXIDOREDUCTASE (EC 1.1.1.6) was purified to homogeneity from a mutant of Escherichia coli K12 that uses this enzyme, instead of ATP:glycerol 3-phosphotransferase (EC 2.7.1.30), as the first enzyme for the dissimilation of glycerol. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate shows a subunit of 39,000 daltons. During electrophoresis under nondenaturing conditions, the protein migrates as two bands. These two forms, both of which are enzymatically active, appear to be dimers and octomers of the same subunit. The optimal pH for the oxidation of glycerol is about 10, and that for the reduction of dihydroxyacetone is about 6. Glycerol dehydrogenation is highly activated by NH4+, K+, or Rb+, but strongly inhibited by N-ethylmalemide, 8-hydroxyquinoline, 1,10-phenanthroline, Cu2+, and Ca2+. The enzyme exhibits a broad substrate specificity. In addition to glycerol, it act on 1,2-propanediol and several of its analogs.