Purification and characterization of cytoplasmic NAD-dependent polypropylene glycol dehydrogenase from Stenotrophomonas maltophilia.

The oxidizing enzyme NAD(+)-dependent polypropylene glycol dehydrogenase (PPG-DH) was purified to homogeneity from the cytoplasmic fraction of Stenotrophomonas maltophilia grown on polypropylene glycol (diol type) 2000. The purified enzyme consisted of a homotetrameric protein (37 kDa subunit) with a molecular mass of around 154 kDa. The N-terminal amino acid sequence (25 residues) showed similarity to the sequences of NAD(+)-dependent secondary alcohol dehydrogenases and NADH-dependent reductases. The enzyme preferentially oxidized medium-chain secondary alcohols, di- and tri-propylene glycols and polypropylene glycols including those with secondary alcohol groups in their molecular structure. Consequently, the enzyme was classified into a group of NAD(+)-dependent secondary alcohol dehydrogenases.