CATH Classification

Domain Context

CATH Clusters

Superfamily Aldolase class I
Functional Family Tryptophan synthase alpha chain, chloroplastic

Enzyme Information

4.2.1.20
Tryptophan synthase.
based on mapping to UniProt P42390
L-serine + 1-C-(indol-3-yl)glycerol 3-phosphate = L-tryptophan + D-glyceraldehyde 3-phosphate + H(2)O.
-!- The alpha-subunit catalyzes the conversion of 1-C-(indol-3- yl)glycerol 3-phosphate to indole and D-glyceraldehyde 3-phosphate (this reaction was listed formerly as EC 4.1.2.8). -!- The indole migrates to the beta-subunit where, in the presence of pyridoxal 5'-phosphate, it is combined with L-serine to form L-tryptophan. -!- In some organisms this enzyme is part of a multifunctional protein that also includes one or more of the enzymes EC 2.4.2.18, EC 4.1.1.48, EC 4.1.3.27 and EC 5.3.1.24. -!- In thermophilic organisms, where the high temperature enhances diffusion and causes the loss of indole, a protein similar to the beta subunit can be found (EC 4.2.1.122). -!- That enzyme cannot combine with the alpha unit of EC 4.2.1.20 to form a complex.
4.1.2.8
Indole-3-glycerol-phosphate lyase.
based on mapping to UniProt P42390
(1S,2R)-1-C-(indol-3-yl)glycerol 3-phosphate = indole + D-glyceraldehyde 3-phosphate.
-!- Forms part of the defense mechanism against insects and microbial pathogens in the grass family, Gramineae, where it catalyzes one of the steps in the formation of the cyclic hydroxamic acids 2,4- dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7- methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA). -!- Resembles the alpha-subunit of EC 4.2.1.20 but, unlike tryptophan synthase, its activity is independent of the beta-subunit and free indole is released.

UniProtKB Entries (1)

P42390
TRPA_MAIZE
Zea mays
Indole-3-glycerol phosphate lyase, chloroplastic

PDB Structure

PDB 1TJR
External Links
Method X-RAY DIFFRACTION
Organism Escherichia
Primary Citation
On the structural basis of the catalytic mechanism and the regulation of the alpha subunit of tryptophan synthase from Salmonella typhimurium and BX1 from maize, two evolutionarily related enzymes.
Kulik, V., Hartmann, E., Weyand, M., Frey, M., Gierl, A., Niks, D., Dunn, M.F., Schlichting, I.
J.Mol.Biol.