EC Number   |
Natural Substrates |
|---|
  2.1.2.13 | 10-formyltetrahydrofolate + UDP-4-amino-4-deoxy-beta-L-arabinopyranose |
- |
| 2.1.2.13 | 10-formyltetrahydrofolate + UDP-4-amino-4-deoxy-beta-L-arabinopyranose |
ArnA is a key enzyme in the 4-amino-4-deoxy-L-arabinose-lipid A modification pathway. It is a bifunctional enzyme catalyzing the oxidative decarboxylation of UDP-glucuronic acid to the UDP-4''-ketopentose (UDP-beta-L-threo-pentapyranosyl-4''-ulose) and the N-10-formyltetrahydrofolate-dependent formylation of UDP-4-amino-4-deoxy-L-arabinose. The transformylase activity of the Escherichia coli ArnA is contained in its 300 N-terminal residues |
| 2.1.2.13 | 10-formyltetrahydrofolate + UDP-4-amino-4-deoxy-beta-L-arabinopyranose |
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-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 L-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 |
| 2.1.2.13 | 10-formyltetrahydrofolate + UDP-4-amino-4-deoxy-beta-L-arabinopyranose |
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 |
