indole-3-glycerol-phosphate synthase
Indole-3-glycerol-phosphate synthase monomer, Mycobacterium tuberculosis
Identifiers
EC no.	4.1.1.48
CAS no.	9031-60-1
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

Indole-3-glycerol phosphate synthase
three-dimensional structure of the bifunctional enzyme phosphoribosylanthranilate isomerase: indoleglycerolphosphate synthase from escherichia coli refined at 2.0 angstroms resolution
Identifiers
Symbol	IGPS
Pfam	PF00218
Pfam clan	CL0036
InterPro	IPR013798
PROSITE	PDOC00536
SCOP2	1pii / SCOPe / SUPFAM
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

The enzyme indole-3-glycerol-phosphate synthase (IGPS) (EC 4.1.1.48) catalyzes the chemical reaction

1-(2-carboxyphenylamino)-1-deoxy-D-ribulose 5-phosphate ${\displaystyle \rightleftharpoons }$ 1-C-(indol-3-yl)-glycerol 3-phosphate + CO₂ + H₂O

This enzyme belongs to the family of lyases, to be specific, the carboxy-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 1-(2-carboxyphenylamino)-1-deoxy-D-ribulose-5-phosphate carboxy-lyase [cyclizing 1-C-(indol-3-yl)glycerol-3-phosphate-forming]. Other names in common use include indoleglycerol phosphate synthetase, indoleglycerol phosphate synthase, indole-3-glycerophosphate synthase, 1-(2-carboxyphenylamino)-1-deoxy-D-ribulose-5-phosphate, and carboxy-lyase (cyclizing). This enzyme participates in phenylalanine, tyrosine and tryptophan biosynthesis and two-component system - general. It employs one cofactor, pyruvate.

Structural studies

In some bacteria, IGPS is a single chain enzyme. In others, such as Escherichia coli, it is the N-terminal domain of a bifunctional enzyme that also catalyses N-(5'-phosphoribosyl)anthranilate isomerase (EC 5.3.1.24) (PRAI) activity, the third step of tryptophan biosynthesis. In fungi, IGPS is the central domain of a trifunctional enzyme that contains a PRAI C-terminal domain and a glutamine amidotransferase (EC 2.4.2.-) (GATase) N-terminal domain.

A structure of the IGPS domain of the bifunctional enzyme from the mesophilic bacterium E. coli (eIGPS) has been compared with the monomeric indole-3-glycerol phosphate synthase from the hyperthermophilic archaeon Sulfolobus solfataricus (sIGPS). Both are single-domain (beta/alpha)8 barrel proteins, with one (eIGPS) or two (sIGPS) additional helices inserted before the first beta strand.^[1]

As of late 2007, 11 structures have been solved for this class of enzymes, with PDB accession codes 1A53, 1I4N, 1J5T, 1JCM, 1JUK, 1JUL, 1LBF, 1LBL, 1PII, 1VC4, and 2C3Z.