1 Administration, Department of Chemistry, Faculty of Science, Københavns Universitet2 Saarland University3 Université de Lorraine4 Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet5 Saarland University6 Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet7 Administration, Department of Chemistry, Faculty of Science, Københavns Universitet
A gene in Bradyrhizobium japonicum USDA 110, annotated as a ribitol dehydrogenase (RDH), had 87 % sequence identity (97 % positives) to the N-terminal 31 amino acids of an L-glucitol dehydrogenase from Stenotrophomonas maltophilia DSMZ 14322. The 729-bp long RDH gene coded for a protein consisting of 242 amino acids with a molecular mass of 26.1 kDa. The heterologously expressed protein not only exhibited the main enantio selective activity with D-glucitol oxidation to D-fructose but also converted L-glucitol to D-sorbose with enzymatic cofactor regeneration and a yield of 90 %. The temperature stability and the apparent K m value for L-glucitol oxidation let the enzyme appear as a promising subject for further improvement by enzyme evolution. We propose to rename the enzyme from the annotated RDH gene (locus tag bll6662) from B. japonicum USDA as a D-sorbitol dehydrogenase (EC 188.8.131.52).
Applied Microbiology and Biotechnology, 2014, Vol 98, Issue 7, p. 3023-3032