|Gene:||sndH||Accession Number: G-10052 (MetaCyc)|
Species: Ketogulonicigenium vulgare DSM 4025
L-Sorbosone dehydrogenase 1 (SNDH 1) is a novel enzyme form Ketogulonicigenium vulgare DSM 4025 (previously known as Gluconobacter oxydans DSM 4025) [Asakura99] that directly converts the furanose ring form (1,4-lactone) of L-sorbosone to L-ascorbate. The enzyme was found to be a homooligomer on gel filtration chromatography, with molecular masses from 150 to 230 kDa. [Miyazaki06].
Two isoforms of this enzyme were also characterized, SNDH2 and SNDH3. SNDH2 was composed of a mixture of 75 and 55 kDa subunits and SNDH3 was composed of 55 kDa subunits. The 55 kDa subunit appeared to be derived from the 75 kDa subunit by C-terminal proteolytic cleavage. It was suggested that the 55 kDa subunit may have biological significance due to its occurrence in cell extracts treated with protease inhibitors and in recombinant Escherichia coli cells (see below) [Miyazaki06].
The sndH gene encoding the 75 kDa gene product was cloned and expressed in Escherichia coli and its activity was demonstrated. Mutants were also constructed and shown to have reduced activity. The deduced amino acid sequence showed 40% identity to a soluble quinoprotein glucose dehydrogenase from Acinetobacter calcoaceticus [Miyazaki06].
Locations: periplasmic space
Molecular Weight of Polypeptide: 65.667 kD (from nucleotide sequence)
Relationship Links: Entrez-Nucleotide:PART-OF:AB205130 , InterPro:IN-FAMILY:IPR008168 , InterPro:IN-FAMILY:IPR009056 , InterPro:IN-FAMILY:IPR011041 , InterPro:IN-FAMILY:IPR011042 , InterPro:IN-FAMILY:IPR012938 , InterPro:IN-FAMILY:IPR019893 , Pfam:IN-FAMILY:PF07995 , Pfam:IN-FAMILY:PF13442 , Prints:IN-FAMILY:PR00605 , Prosite:IN-FAMILY:PS51007
|Cellular Component:||GO:0030288 - outer membrane-bounded periplasmic space [Miyazaki06]|
Enzymatic reaction of: L-sorbosone dehydrogenase
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.
The reaction is favored in the direction shown.
In Pathways: L-ascorbate biosynthesis III
The reaction product, L-ascorbate, was identified by HPLC. No activity was found with L-sorbose, D-sorbitol, or L-gulono-γ-lactone as substrate. Aldose substrates gave high activity. Metal ions did not enhance activity. The enzyme also produced 2-keto-L-gulonate (2-keto-D-gluconate) from L-sorbosone, probably from the spontaneously formed L-sorbosone 2,6-lactone tautomer of L-sorbosone. [Miyazaki06].
T(opt): 20-40 °C [Miyazaki06]
pH(opt): 7-8 [Miyazaki06]
Miyazaki06: Miyazaki T, Sugisawa T, Hoshino T (2006). "Pyrroloquinoline quinone-dependent dehydrogenases from Ketogulonicigenium vulgare catalyze the direct conversion of L-sorbosone to L-ascorbic acid." Appl Environ Microbiol 72(2);1487-95. PMID: 16461703
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