Glycerol dehydrogenase (EC 1.1.1.6, also known as NAD⁺-linked glycerol dehydrogenase, glycerol: NAD⁺ 2-oxidoreductase, GDH, GlDH, GlyDH) is an enzyme in the oxidoreductase family that utilizes the NAD⁺ to catalyze the oxidation of glycerol to form glycerone (dihydroxyacetone).

This enzyme is an oxidoreductase, specifically a metal-dependent alcohol dehydrogenase that plays a role in anaerobic glycerol metabolism and has been isolated from a number of bacteria, including Enterobacter aerogenes,Klebsiella aerogenes,Streptococcus faecalis,Erwinia aeroidea,Bacillus megaterium, and Bacillus stearothermophilus. However, most studies of glycerol dehydrogenase have been performed in Bacillus stearothermophilus, (B. stearothermophilus) due to its thermostability and the following structural and functional information will, therefore, refer primarily to the characterization of the enzyme in this bacterium.

Glycerol dehydrogenase is a homooctamer composed of eight identical monomer subunits made up of a single polypeptide chain of 370 amino acids (molecular weight 42,000 Da). Each subunit contains 9 beta sheets and 14 alpha helices within two distinct domains (N-terminal, residues 1-162 and C-terminal, residues 163-370). The deep cleft formed between these two domains serves as the enzyme’s active site. This active site consists of one bound metal ion, one NAD⁺ nicotinamide ring binding site, and a substrate binding site.

Research into the structure of B. stearothermophilus shows that the active site contains a divalent cation—zinc ion, Zn²⁺. This zinc ion forms tetrahedral dipole interactions between the amino acid residues Asp173, His256, and His274 as well as a water molecule.

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