ID 4.2.1.168 DE GDP-4-dehydro-6-deoxy-alpha-D-mannose 3-dehydratase. CA GDP-4-dehydro-alpha-D-rhamnose + L-glutamate = 2-oxoglutarate + GDP-4- CA dehydro-3,6-dideoxy-alpha-D-mannose + NH4(+). CC -!- This enzyme, involved in beta-L-colitose biosynthesis, is a unique CC vitamin-B6-dependent enzyme. CC -!- In the first step of catalysis, the bound pyridoxal phosphate (PLP) CC cafactor is transaminated to the pyridoxamine 5'-phosphate (PMP) form CC of vitamin B6, using L-glutamate as the amino group donor. CC -!- The PMP cofactor then forms a Schiff base with the sugar substrate CC and the resulting adduct undergoes a 1,4-dehydration to eliminate the CC 3-OH group. CC -!- Hydrolysis of the product from the enzyme restores the PLP cofactor CC and results in the release of an unstable enamine intermediate. CC -!- This intermediate tautomerizes to form an imine form, which CC hydrolyzes spontaneously, releasing ammonia and forming the final CC product. DR D3QY10, COLD_ECOCB ; G4WJD4, COLD_YERPU ; //