IUBMB Enzyme Nomenclature


Accepted name: aminodeoxychorismate synthase

Reaction: chorismate + L-glutamine = 4-amino-4-deoxychorismate + L-glutamate (overall reaction)
(1a) L-glutamine + H2O = L-glutamate + NH3
(1b) chorismate + NH3 = 4-amino-4-deoxychorismate + H2O

For diagram of reaction click here

Other name(s): ADC synthase; 4-amino-4-deoxychorismate synthase; PabAB; chorismate:L-glutamine amido-ligase (incorrect)

Systematic name: chorismate:L-glutamine aminotransferase

Comments: The enzyme is composed of two parts, a glutaminase (PabA in Escherichia coli) and an aminotransferase (PabB). In the absence of PabA and glutamine (but in the presence of Mg2+), PabB can convert ammonia and chorismate into 4-amino-4-deoxychorismate. PabA converts glutamine into glutamate only in the presence of stoichiometric amounts of PabB. In many organisms, including plants, the genes encoding the two proteins have fused to encode a single bifunctional protein. This enzyme is coupled with EC, aminodeoxychorismate lyase, to form 4-aminobenzoate. cf. EC, 4-amino-4-deoxychorismate synthase (2-amino-4-deoxychorismate-forming).

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number:


1. Ye, Q.Z., Liu, J. and Walsh, C.T. p-Aminobenzoate synthesis in Escherichia coli: purification and characterization of PabB as aminodeoxychorismate synthase and enzyme X as aminodeoxychorismate lyase. Proc. Natl. Acad. Sci. USA 87 (1990) 9391-9395. [PMID: 2251281]

2. Viswanathan, V.K., Green, J.M. and Nichols, B.P. Kinetic characterization of 4-amino 4-deoxychorismate synthase from Escherichia coli. J. Bacteriol. 177 (1995) 5918-5923. [PMID: 7592344]

3. Chang, Z., Sun, Y., He, J. and Vining, L.C. p-Aminobenzoic acid and chloramphenicol biosynthesis in Streptomyces venezuelae: gene sets for a key enzyme, 4-amino-4-deoxychorismate synthase. Microbiology (Reading) 147 (2001) 2113-2126. [PMID: 11495989]

4. Camara, D., Richefeu-Contesto, C., Gambonnet, B., Dumas, R. and Rebeille, F. The synthesis of pABA: Coupling between the glutamine amidotransferase and aminodeoxychorismate synthase domains of the bifunctional aminodeoxychorismate synthase from Arabidopsis thaliana. Arch. Biochem. Biophys. 505 (2011) 83-90. [PMID: 20851095]

[EC created 2003 as EC, transferred 2007 to EC, modified 2022]

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