Accepted name: UDP-4-amino-4-deoxy-L-arabinose formyltransferase
Reaction: 10-formyltetrahydrofolate + UDP-4-amino-4-deoxy-β-L-arabinopyranose = 5,6,7,8-tetrahydrofolate + UDP-4-deoxy-4-formamido-β-L-arabinopyranose
Other name(s): UDP-L-Ara4N formyltransferase; ArnAFT
Systematic name: 10-formyltetrahydrofolate:UDP-4-amino-4-deoxy-β-L-arabinose N-formyltransferase
Comments: The activity is part of a bifunctional enzyme also performing the reaction of EC [UDP-glucuronic acid dehydrogenase (UDP-4-keto-hexauronic acid decarboxylating)].
1.  Breazeale, S.D., Ribeiro, A.A., McClerren, A.L. and Raetz, C.R.H. A formyltransferase required for polymyxin resistance in Escherichia coli and the modification of lipid A with 4-amino-4-deoxy-L-arabinose. Identification and function of UDP-4-deoxy-4-formamido-L-arabinose. J. Biol. Chem. 280 (2005) 14154–14167. [PMID: 15695810]
2.  Gatzeva-Topalova, P.Z., May, A.P. and Sousa, M.C. Crystal structure and mechanism of the Escherichia coli ArnA (PmrI) transformylase domain. An enzyme for lipid A modification with 4-amino-4-deoxy-L-arabinose and polymyxin resistance. Biochemistry 44 (2005) 5328–5338. [PMID: 15807526]
3.  Williams, G.J., Breazeale, S.D., Raetz, C.R.H. and Naismith, J.H. Structure and function of both domains of ArnA, a dual function decarboxylase and a formyltransferase, involved in 4-amino-4-deoxy-L-arabinose biosynthesis. J. Biol. Chem. 280 (2005) 23000–23008. [PMID: 15809294]
4.  Gatzeva-Topalova, P.Z., May, A.P. and Sousa, M.C. Structure and mechanism of ArnA: conformational change implies ordered dehydrogenase mechanism in key enzyme for polymyxin resistance. Structure 13 (2005) 929–942. [PMID: 15939024]
5.  Yan, A., Guan, Z. and Raetz, C.R.H. An undecaprenyl phosphate-aminoarabinose flippase required for polymyxin resistance in Escherichia coli. J. Biol. Chem. 282 (2007) 36077–36089. [PMID: 17928292]
[EC created 2010]
Accepted name: indolylacetylinositol arabinosyltransferase
Reaction: UDP-L-arabinose + (indol-3-yl)acetyl-1D-myo-inositol = UDP + (indol-3-yl)acetyl-myo-inositol 3-L-arabinoside
Other name(s): arabinosylindolylacetylinositol synthase; UDP-L-arabinose:indol-3-ylacetyl-myo-inositol L-arabinosyltransferase; UDP-L-arabinose:(indol-3-yl)acetyl-myo-inositol L-arabinosyltransferase
Systematic name: UDP-L-arabinose:(indol-3-yl)acetyl-1D-myo-inositol L-arabinosyltransferase
Comments: The position of acylation is indeterminate because of the ease of acyl transfer between hydroxy groups. For a diagram showing the biosynthesis of UDP-L-arabinose, click here.
1.  Corcuera, L.J. and Bandurski, R.S. Biosynthesis of indol-3-yl-acetyl-myo-inositol arabinoside in kernels of Zea mays L. Plant Physiol. 70 (1982) 1664–1666. [PMID: 16662740]
[EC created 1986, modified 2003]
Accepted name: UDP-4-amino-4-deoxy-L-arabinose aminotransferase
Reaction: UDP-4-amino-4-deoxy-β-L-arabinopyranose + 2-oxoglutarate = UDP-β-L-threo-pentapyranos-4-ulose + L-glutamate
Other name(s): UDP-(β-L-threo-pentapyranosyl-4′′-ulose diphosphate) aminotransferase; UDP-4-amino-4-deoxy-L-arabinose—oxoglutarate aminotransferase; UDP-Ara4O aminotransferase; UDP-L-Ara4N transaminase
Systematic name: UDP-4-amino-4-deoxy-β-L-arabinose:2-oxoglutarate aminotransferase
Comments: A pyridoxal 5′-phosphate enzyme.
1.  Breazeale, S.D., Ribeiro, A.A. and Raetz, C.R. Origin of lipid A species modified with 4-amino-4-deoxy-L-arabinose in polymyxin-resistant mutants of Escherichia coli. An aminotransferase (ArnB) that generates UDP-4-deoxyl-L-arabinose. J. Biol. Chem. 278 (2003) 24731–24739. [PMID: 12704196]
2.  Noland, B.W., Newman, J.M., Hendle, J., Badger, J., Christopher, J.A., Tresser, J., Buchanan, M.D., Wright, T.A., Rutter, M.E., Sanderson, W.E., Muller-Dieckmann, H.J., Gajiwala, K.S. and Buchanan, S.G. Structural studies of Salmonella typhimurium ArnB (PmrH) aminotransferase: a 4-amino-4-deoxy-L-arabinose lipopolysaccharide-modifying enzyme. Structure 10 (2002) 1569–1580. [PMID: 12429098]
[EC created 2010]
Accepted name: UTP-monosaccharide-1-phosphate uridylyltransferase
Reaction: UTP + a monosaccharide 1-phosphate = diphosphate + UDP-monosaccharide
Glossary: UDP-Xyl = UDP-α-D-xylose
UDP-L-Ara = UDP-β-L-arabinopyranose
Other name(s): UDP-sugar pyrophosphorylase; PsUSP
Comments: Requires Mg2+ or Mn2+ for maximal activity. The reaction can occur in either direction and it has been postulated that MgUTP and Mg-diphosphate are the actual substrates [1,2]. The enzyme catalyses the formation of UDP-Glc, UDP-Gal, UDP-GlcA, UDP-L-Ara and UDP-Xyl, showing broad substrate specificity towards monosaccharide 1-phosphates. Mannose 1-phosphate, L-Fucose 1-phosphate and glucose 6-phosphate are not substrates and UTP cannot be replaced by other nucleotide triphosphates [1].
1.  Kotake, T., Yamaguchi, D., Ohzono, H., Hojo, S., Kaneko, S., Ishida, H.K. and Tsumuraya, Y. UDP-sugar pyrophosphorylase with broad substrate specificity toward various monosaccharide 1-phosphates from pea sprouts. J. Biol. Chem. 279 (2004) 45728–45736. [PMID: 15326166]
2.  Rudick, V.L. and Weisman, R.A. Uridine diphosphate glucose pyrophosphorylase of Acanthamoeba castellanii. Purification, kinetic, and developmental studies. J. Biol. Chem. 249 (1974) 7832–7840. [PMID: 4430676]
[EC created 2006]
Accepted name: UDP-galacturonate decarboxylase
Reaction: UDP-D-galacturonate = UDP-L-arabinose + CO2
Other name(s): UDP-galacturonic acid decarboxylase; UDPGalUA carboxy lyase; UDP-D-galacturonate carboxy-lyase
Systematic name: UDP-D-galacturonate carboxy-lyase (UDP-L-arabinose-forming)
1.  Fan, D.-F. and Feingold, D.S. UDPgalacturonic acid decarboxylase from Ampullariella digitata. Methods Enzymol. 28B (1972) 438–439.
[EC created 1984]
Accepted name: UDP-arabinose 4-epimerase
Reaction: UDP-L-arabinose = UDP-D-xylose
Other name(s): uridine diphosphoarabinose epimerase; UDP arabinose epimerase; uridine 5′-diphosphate-D-xylose 4-epimerase; UDP-D-xylose 4-epimerase
Systematic name: UDP-L-arabinose 4-epimerase
1.  Feingold, D.S., Neufeld, E.F. and Hassid, W.Z. The 4-epimerization and decarboxylation of uridine diphosphate D-glucuronic acid by extracts from Phaseolus aureus seedlings. J. Biol. Chem. 235 (1960) 910–913. [PMID: 13821949]
[EC created 1965]