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. Author manuscript; available in PMC: 2009 May 12.
Published in final edited form as: Biochemistry. 2004 Oct 26;43(42):13370–13379. doi: 10.1021/bi048551f

FIGURE 1.

FIGURE 1

Proposed pathway for the biosynthesis of UDP-Ara4N. The pathway starts with Ugd/PmrE oxidizing UDP-Glc to UDP-GlcA. UDP-GlcA is then oxidized at position 4 by the C-terminal domain of ArnA to yield the UDP-4-keto glucuronic acid intermediate that is then decarboxylated to UDP-4-keto arabinose by the same enzyme. UDP-Ara4O is transaminated by ArnB yielding the novel sugar-nucleotide UDP-4-amino-4-deoxy-arabinose (UDP-Ara4N). The N-terminal domain of ArnA can formylate UDP-Ara4N and has been proposed to help displace the reaction catalyzed by ArnB toward UDP-Ara4N synthesis and generate a transiently formylated product (21).