Indole-3-glycerol phosphate lyase

Evolution of an Indole-3-glycerol Phosphate Lyase Function. 72... 

EVOLUTION OF AN INDOLE-3-GLYCEROL PHOSPHATE LYASE FUNCTION... 

Figure 4.2 Functional comparison of the indole-3-glycerole phosphate lyases IGL and BXI with the tryptophan synthase complex.

The synthesis of several other plant metabolites, such as auxin, indole glucosinolates, anthranilate-derived alkaloids, and tryptamine derivatives, could depend on indole as an intermediate. Indole is also found in the scent of flowers such as lilac and robinia. Therefore, it is possible that the recruitment of an indole-3-glycerol phosphate lyase function from TSA genes might have occurred independently several times during plant evolution. 

Tryptophan synthase (TS) catalyzes the ultimate step in tryptophan biosynthesis (details see Fig. 4.2). Indole and benzoxazinoid secondary metabolite formation branches from this pathway. The two lyases IGL and BXl cleave indole-3-glycerol phosphate into indole (and glycerolaldehyde-3-phosphate, not shown) and serve as committing enzymes for indole derived secondary metabolites. Indole produced by IGL directly functions as volatile signal. Indole produced by BXl is converted by other enzymes (BX2-BX9) to benzoxazinoids that have an important function in the chemical defense of grasses. 

L-Tryptophan synthase, tryptophan desmolase, L-serine hydro-lyase (adding imhleglycerol-phos-phate) (EC 4.2.1.20) the enzyme catalysing the synthesis of L-tryptophan from L-serine and indole 3-glycerol phosphate. T.s. from E. coli (M, 149,000) and other prokaryotes has 02 subunit composition. The enzyme separates easily into monomeric subunit a (also called protein B, M, 29,000) and dimeric subunit 02 (also called protein B Af, of dimer 90,000) when eluted from DEAE cellulose with a sodium chloride gradient. The separated subunits catalyse partial reactions of L-tryptophan synthesis ... 

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