Indole glycerol

Phosphoribosyl anthranilate isomerase Indole glycerol phosphate synthase (E.C. 4.1.2.8)... 

Subsequently Yanofsky (233) separated the enzymes involved in the conversion of anthranilic add to indole into two fractions and isolated the intermediate reaction product, indole 3-glycerol phosphate. One of the enzyme bactions, indole glycerol phosphate thetase, catalyzed the formation of indole 3-glyoraol phoqihate as shown in reaction 1, Fig. 15. 

Magnesium ions are required by this enzyme system. In place of phos-phoribosylpyrophosphate, ribose 5-phosphate and ATP can be substituted, but the synthesis proceeds at a lower rate. With ribose 5-phospbate there is an absolute requirement for phosphate ion. Experiments with P showed that the terminal phosphate of indole glycerol phosphate was derived from the terminal phosphate of phosphoribosylp3Tophosphate. The second enzyme fraction, indole glycerol phosphate hydrolase, cleaves indole glycerol phosphate to indole and a triose phosphate. The triose phosphate appears to be 3-phosphoglyceraldehyde. The reaction may therefore be written as shown in reaction 3, Fig. 15. 

Yanofsky (SS3) postulated that the initial reaction of PP-ribose-P with anthranilic acid would form W-0-carboxyphenyl-D-ribosylamine-5-P (reaction 1, Fig. 15). By dehydration and an Amadori-type rearrangement there would be formed anthranilic deoxyribonucleotide (reaction 2, Fig. 15). This would then yield indole glycerol phosphate by decarboxylation and loss of the hydroxy group on C-2 of the ribulose phosphate side chain. 

Smith and Yanofsky ZSSh) in a study of the formation of indole glycerol phosphate from anthranilic acid and PP-ribosyl-P determined that an intermediate product was formed with one type of tr3q>tophanless bacterial mutant that retained the carboxyl group of anthranilic acid (labeled with C ). These authors also prepared anthranilic deoxyribonucleotide S3mthetically and demonstrated that it was converted to indole glycerol-P by extracts of bacteria that accumulate the latter. No cofactor requirements were observed. The synthetic product was similar to the material in the culture filtrates, in being acid-stable and alkali-labile. Dephosphorylation with phosphatase yields a product that appeared to be anthranilic deoxyriboside. 

The indole glycerol phosphate was isolated and purified by a sequence of reactions involving adsorption on charcoal and elution with ammoniated alcohol, precipitation as the barium salt, and chromatography on Dowex 1 (Cl ) and charcoal. The identity of the product was established by the usual methods of organic chemistry. 

Figure 4.6 The bifunctional enzyme PRA-isomerase (PRAI) IGP-synthase (IGPS) catalyzes two sequential reactions in the biosynthesis of tryptophan. In the first reaction (top half), which is catalyzed by the C-terminal PRAI domain of the enzyme, the substrate N-(5 -phosphoribosyl) anthranilate (PRA) is converted to l-(o-carboxyphenylamino)-l-deoxyribulose 5-phosphate (CdRP) by a rearrangement reaction. The succeeding step (bottom half), a ring closure reaction from CdRP to indole-3-glycerol phosphate (IGP), is catalyzed by the N-terminal IGPS domain.

Priestle, J.P, et al. Three-dimensional structure of the bifunctional enzyme N-(5 -phosphoribosyl) anthranilate isomerase-indole-3-glycerol-phosphate synthase from Escheriehia eoli. Proc. Natl. Aead. 

Chemistry and biological properties of polyfunctional indole-3-carbinol derivatives [l-(indol-3-yl)glycerols and related compounds, (3-hydroxytryptamines, and ascorbigens] 95F369. 

Interestingly, the Fischer indole synthesis does not easily proceed from acetaldehyde to afford indole. Usually, indole-2-carboxylic acid is prepared from phenylhydrazine with a pyruvate ester followed by hydrolysis. Traditional methods for decarboxylation of indole-2-carboxylic acid to form indole are not environmentally benign. They include pyrolysis or heating with copper-bronze powder, copper(I) chloride, copper chromite, copper acetate or copper(II) oxide, in for example, heat-transfer oils, glycerol, quinoline or 2-benzylpyridine. Decomposition of the product during lengthy thermolysis or purification affects the yields. 

Analogous results for the temperature dependence of tR have been obtained in fluorescence studies of indole and tryptophan in glycerol/24,33) Therefore, the above approach may be considered to be adequate for the description of the dynamics of the model viscous media. 

This enzyme [EC 2.4.2.18], also referred to as phospho-ribosyl-anthranilate pyrophosphorylase, catalyzes the reaction of anthranilate with phosphoribosylpyrophos-phate to produce A-5 -phosphoribosylanthranilate and pyrophosphate. In certain species, this enzyme is part of a multifunctional protein, together with one or more other components of the system for the biosynthesis of tryptophan (i.e., indole-3-glycerol-phosphate synthase, anthranilate synthase, tryptophan synthase, and phos-phoribosylanthranilate isomerase). 

This pyridoxal-phosphate-dependent enzyme [EC 4.2.1.20] catalyzes the reaction of L-serine with l-(indol-3-yl)glycerol 3-phosphate to produce L-tryptophan and glyceraldehyde 3-phosphate. The enzyme will also catalyze (a) the conversion of serine and indole into tryptophan and water and (b) conversion of indoleglycerol phosphate into indole and glyceraldehyde phosphate. 

Figure 19.24 A real folding funnel. Refolding chromatography of IGPS (49-252) (indole 3-glycerol phosphate synthase lacking residues 1 -48). Denatured IGPS from an inclusion body was dissolved in 8-M urea and diluted onto a 3-mL column of a GroEL minichaperone (GroEF) that was immobilized on agarose. Ninety-six percent of the protein eluted as fully active material.

Indole 3-glycerol phosphate —indole + glyceraldehye 3-phosphate (1,4)... 

Besides having a noncovalent association of subunits as in tryptophan synthase, some enzymes are double-headed, in that they contain two distinct activities in a single polypeptide chain. A good example of this is the indole 3-glycerol phosphate-synthase-phosphoribosyl anthranilate isomerase bifunc-tional enzyme from the tryptophan operon of E. coli. The crystal structure of the complex has been solved at 2.0 A resolution.39 The two enzymes have been separated by genetic manipulation.40 The activity of the two separate monomeric monofunctional constituents is the same as in the covalent complex so there is no catalytic advantage of having the proteins fused. 

The two intermediates in the conversion of anthranilate to indole-3-glycerol phosphate, phosphoribosylan-thranilate and l -(O-carboxyphenylamino)-1 -deoxyribu-lose-5 phosphate, were originally postulated to account for the involvement of phosphoribosyl pyrophosphate in indole-3-glycerol phosphate formation. Support for the postulate was obtained when the dephosphorylated derivative of the second of these intermediates was found in the culture fluids of certain tryptophan-requiring bacterial mutants. The corresponding derivative of the first intermediate has not been found, probably because of its instability. Indeed, this compound, when formed in extracts, is rapidly broken down to anthranilate and ribose-5-phosphate. 

C indole-3-glycerol phosphate synthase none decarboxylative closure of the indole ring... 

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