Abstract: The present invention has an object to provide a D-mannose isomerase of membrane-bound form having the optimal reaction pH in acidic region. The membrane-bound D-mannose isomerase derived from acetic acid bacteria is produced. The acetic acid bacteria are preferably belong to the genera of Acetobacter, Gluconobacter, or Gluconacetobacter. Furthermore, the membrane-bound D-mannose isomerase from the acetic acid bacteria is used to produce D-fructose from D-mannose.

Abstract: The present invention provides a microorganism obtainable by introducing a DNA coding for NADH dehydrogenase constituting a NADH dehydrogenase complex whose number of dischargeable proton molecules per electron is zero among NADH dehydrogenase complexes functioning as a proton pump in electron transport systems of aerobic bacteria, and an industrially advantageous process for producing an amino acid using the microorganism.

Abstract: Pyrroloquinoline quinone-dependent glycerol dehydrogenase is provided which requires no surfactant for its solubilization and stabilization. The glycerol dehydrogenase has the following properties:(a) catalyzing the following reaction:glycerol+electron acceptor.fwdarw.glyceraldehyde+reduced electron acceptor,(b) optimum pH: pH 8-9,(c) pH stability: stable at pH 7-11,(d) optimum temperature: 20.degree.-25.degree. C,(e) thermal stability: stable at a temperature of 30.degree. C or less for 10 minutes at a pH of 7.0,(f) molecular weight: 70,000 by gel filtration and SDS polyacrylamide gel electrophoresis,(g) bound to pyrroloquinoline quinone as a prosthetic group,(h) soluble and stable without the need of an ionic or non-ionic surfactant.

Abstract: Pyrroquinoline quinone-dependent glycerol dehydrogenase is provided which requires no surfactant for its solubilization and stabilization. The glycerol dehydrogenase has the following properties:(a) catalyzing the following reaction: glycerol+electron acceptor.dbd.glyceraldehyde+reduced electron acceptor,(b) optimum pH: pH 8-9,(c) pH stability: stable at pH 7-11,(d) optimum temperature: 20.degree.-25.degree. C.,(e) thermal stability: stable at a temperature of 30.degree. C. or less for 10 minutes at a pH of 7.0,(f) molecular weight: 70,000 by gel filtration and SDS polyacrylamide gel electrophoresis,(g) bound to pyrroloquinoline quinone as a prosthetic group,(h) soluble and stable without the need of an ionic or non-ionic surfactant.