{PDOC00536}
{PS00614; IGPS}
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* Indole-3-glycerol phosphate synthase signature *
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Indole-3-glycerol phosphate synthase (EC 4.1.1.48) (IGPS) catalyzes the fourth
step in the biosynthesis  of  tryptophan:  the  ring  closure of 1-(2-carboxy-
phenylamino)-1-deoxyribulose into indol-3-glycerol-phosphate.

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  catalyzes  N-(5'-phosphoribosyl)anthranilate isomerase (PRAI)  activity,
the third  step  of  tryptophan  biosynthesis.  In  fungi, IGPS is the central
domain of a trifunctional  enzyme  that also contains a PRAI C-terminal domain
and a glutamine amidotransferase N-terminal domain.

The N-terminal  section of IGPS contains a highly conserved region which X-ray
crystallography studies  [1]  have shown to be part of the active site cavity.
We use this region as a signature pattern for IGPS.

-Consensus pattern: [LIVMFY]-[LIVMC]-x-E-[LIVMFYC]-K-[KRSPQV]-[STAHKRYC]-S-P-
                    [STRK]-x(3,7)-[LIVMFYST]
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for Phytophthora parasitica IGPS which lack this region.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: April 2006 / Pattern revised.

[ 1] Wilmanns M., Priestle J.P., Niermann T., Jansonius J.N.
     "Three-dimensional structure of the bifunctional enzyme
     phosphoribosylanthranilate isomerase: indoleglycerolphosphate synthase
     from Escherichia coli refined at 2.0 A resolution."
     J. Mol. Biol. 223:477-507(1992).
     PubMed=1738159

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