Information on EC 4.2.1.168 - GDP-4-dehydro-6-deoxy-alpha-D-mannose 3-dehydratase

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     4 Lyases
         4.2 Carbon-oxygen lyases
             4.2.1 Hydro-lyases
                4.2.1.168 GDP-4-dehydro-6-deoxy-alpha-D-mannose 3-dehydratase
IUBMB Comments
This enzyme, involved in beta-L-colitose biosynthesis, is a unique vitamin-B6-dependent enzyme. In the first step of catalysis, the bound pyridoxal phosphate (PLP) cafactor is transaminated to the pyridoxamine 5'-phosphate (PMP) form of vitamin B6, using L-glutamate as the amino group donor. The PMP cofactor then forms a Schiff base with the sugar substrate and the resulting adduct undergoes a 1,4-dehydration to eliminate the 3-OH group. Hydrolysis of the product from the enzyme restores the PLP cofactor and results in the release of an unstable enamine intermediate. This intermediate tautomerizes to form an imine form, which hydrolyses spontaneously, releasing ammonia and forming the final product.
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The enzyme appears in viruses and cellular organisms
Synonyms
colD, GDP-4-keto-6-deoxy-D-mannose-3-dehydratase, WbdK, more
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
2-GDP-[(2S,3S,6R)-5-amino-6-methyl-3,6-dihydro-2H-pyran-3-ol] = 2-GDP-[(2S,3S,6R)-5-imino-6-methyloxan-3-ol]
show the reaction diagram
(1b), spontaneous
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GDP-2-[(2S,3S,6R)-5-imino-6-methyloxan-3-ol] + H2O = GDP-4-dehydro-3,6-dideoxy-alpha-D-mannose + NH3
show the reaction diagram
(1c), spontaneous
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GDP-4-dehydro-alpha-D-rhamnose + L-glutamate = 2-GDP-[(2S,3S,6R)-5-amino-6-methyl-3,6-dihydro-2H-pyran-3-ol] + 2-oxoglutarate + H2O
show the reaction diagram
(1a)
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GDP-4-dehydro-alpha-D-rhamnose + L-glutamate = GDP-4-dehydro-3,6-dideoxy-alpha-D-mannose + 2-oxoglutarate + NH3
show the reaction diagram
overall reaction
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PATHWAY SOURCE
PATHWAYS
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