1.1.1.305: UDP-glucuronic acid dehydrogenase (UDP-4-keto-hexauronic acid decarboxylating)
This is an abbreviated version!
For detailed information about UDP-glucuronic acid dehydrogenase (UDP-4-keto-hexauronic acid decarboxylating), go to the full flat file.
Reaction
Synonyms
ArnA, ArnA dehydrogenase, ArnADH, RsU4kpxs, UDP-alpha-D-xylose synthase, UDP-GlcUA dehydrogenase, UGA decarboxylase, UXS
ECTree
1.1.1.305 UDP-glucuronic acid dehydrogenase (UDP-4-keto-hexauronic acid decarboxylating)Advanced search results
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results (Natural Substrates Products
Natural Substrates Products on EC 1.1.1.305 - UDP-glucuronic acid dehydrogenase (UDP-4-keto-hexauronic acid decarboxylating)
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NATURAL SUBSTRATE 
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
UDP-alpha-D-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
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r
UDP-alpha-D-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
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-
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r
UDP-alpha-D-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
-
-
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?
UDP-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
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-
-
?
UDP-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
-
ArnA is a bi-functional enzyme, the oxidative decarboxylation of UDP-glucuronic acid is catalyzed by the 345-residue C-terminal domain of ArnA. The 304-residue N-terminal domain catalyzes the N-10-formyltetrahydrofolate-dependent formylation of the 4''-amine of UDP-L-4-amino-4-deoxy-L-arabinose, generating the sugar nucleotide, uridine 5'-diphospho-beta-(4-deoxy-4-formamido-L-arabinose). The two domains of ArnA are expressed independently as active proteins in Escherichia coli. Both are required for maintenance of polymyxin resistance and 4-amino-4-deoxy-L-arabinose modification of lipid A. only the formylated sugar nucleotide is converted in vitro to an undecaprenyl phosphate-linked form by the enzyme ArnC
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?
UDP-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
ArnA is a key enzyme in the lipid A modification pathway, and its deletion abolishes both the Ara4N-lipid A modification and polymyxin resistance. ArnA is a bifunctional enzyme. It can catalyze the NAD+-dependent decarboxylation of UDP-glucuronic acid to UDP-4-keto-arabinose and the N-10-formyltetrahydrofolate dependent formylation of UDP-4-amino-4-deoxy-L-arabinose
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?
UDP-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
modification of the lipid A moiety of lipopolysaccharide by the addition of the sugar 4-amino-4-deoxy-L-arabinose is a strategy adopted by pathogenic Gram-negative bacteria to evade cationic antimicrobial peptides produced by the innate immune system. The bifunctional enzyme ArnA is required for 4-amino-4-deoxy-L-arabinose biosynthesis and catalyzes the NAD+-dependent oxidative decarboxylation of UDP-glucuronic acid to generate a UDP-4'-keto-pentose sugar and also catalyzes transfer of a formyl group from N-10-formyltetrahydrofolate to the 4'-amine of UDP-4-amino-4-deoxy-L-arabinose
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?
UDP-glucuronate + NAD+
UDP-beta-L-threo-pentapyranos-4-ulose + CO2 + NADH + H+
the modification of lipid A with 4-amino-4-deoxy-L-arabinose allows gram-negative bacteria to resist the antimicrobial activity of cationic antimicrobial peptides and antibiotics such as polymyxin. ArnA is the first enzyme specific to the lipid A-Ara4N pathway. It contains two functionally and physically separable domains: a dehydrogenase domain (ArnA_DH) catalyzing the NAD+-dependent oxidative decarboxylation of UDP-glucuronic acid, and a transformylase domain that formylates UDP-4-amino-4-deoxy-L-arabinose
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?
additional information
?
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UGA decarboxylase produces NADH and UDP-alpha-D-4-dehyroxylose as products, it can rebind NADH and UDP-alpha-D-4-dehyroxylose to slowly make UDP-alpha-D-xylose
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additional information
?
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one activity is to decarboxylate UDP-glucuronic acid to UDP-beta-L-threo-pentopyranosyl-4-ulose in the presence of NAD+. The second activity converts UDP-beta-L-threo-pentopyranosyl-4-ulose and NADH to UDP-xylose and NAD+, albeit at a lower rate. Following decarboxylation, there is stereospecific protonation at the C5pro-R position
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