Nucleotide sequence, cloning, and overexpression of the D-threonine dehydrogenase gene from Pseudomonas cruciviae

D-Threonine dehydrogenase (EC 1.1.1) catalyses the oxidation of the 3-hydroxyl group of D-threonine. The nucleotide sequence of the structural gene, dtdS, for this enzyme from Pseudomonas cruciviae IFO 12047 was determined. The dtdS gene encodes a 292 amino acid polypeptide. The enzyme was overproduced in Escherichia coli cells; the activity was found in cell extracts of the clone. The enzyme showed high sequence similarity to 3-hydroxyisobutyrate dehydrogenases. This is the first example showing the primary structure of an enzyme catalysing the NADP(+)-dependent dehydrogenation of D-threo-3-hydroxyamino acids.