2.5.1.97: pseudaminic acid synthase
This is an abbreviated version!
For detailed information about pseudaminic acid synthase, go to the full flat file.
Reaction
Synonyms
NeuB3, PseG, PseI
ECTree
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Substrates Products
Substrates Products on EC 2.5.1.97 - pseudaminic acid synthase
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REACTION DIAGRAM
phosphoenolpyruvate + 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose + H2O
phosphate + 5,7-bis(acetylamino)-3,5,7,9-tetradeoxy-L-glycero-alpha-L-manno-2-nonulopyranosonic acid
additional information
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N-acetyl-D-mannosamine can not replace 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose as a substrate indicating that the enzyme does not possess detectable sialic acid synthase activity
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phosphate + 5,7-bis(acetylamino)-3,5,7,9-tetradeoxy-L-glycero-alpha-L-manno-2-nonulopyranosonic acid
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pseudaminic acid biosynthesis
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phosphoenolpyruvate + 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose + H2O
phosphate + 5,7-bis(acetylamino)-3,5,7,9-tetradeoxy-L-glycero-alpha-L-manno-2-nonulopyranosonic acid
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phosphoenolpyruvate attacks the si-face of the aldehyde of 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose to generate an (S)-configuration at C-4. The proposed catalytic mechanism of pseudaminic acid synthase is the attack of the C-3 of PEP to the aldehyde of the open chain form of 6-deoxy-AltdiNAc and an attack of water to the C-2 of phosphoenolpyruvate to form a tetrahedral intermediate. The tetrahedral intermediate then collapses to release inorganic phosphate and form the open chain form of pseudaminic acid that cyclizes to the pyranose form in solution
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phosphoenolpyruvate + 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose + H2O
phosphate + 5,7-bis(acetylamino)-3,5,7,9-tetradeoxy-L-glycero-alpha-L-manno-2-nonulopyranosonic acid
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pseudaminic acid biosynthesis
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phosphoenolpyruvate + 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose + H2O
phosphate + 5,7-bis(acetylamino)-3,5,7,9-tetradeoxy-L-glycero-alpha-L-manno-2-nonulopyranosonic acid
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combining the five enzymes of pseudaminic acid biosynthesis (PseB, PseC, PseH, PseG, PseI) in a one-pot reaction results in 100% conversion of UDP-N-acetylglucosamine to pseudaminic acid after 20 h
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