Anthranilate synthase-phosphoribosyltransferase

The first two steps in the biosynthesis of tryptophan in Salmonella typhimurium involve the enzyme complex anthranilate synthase-phosphoribosyltransferase, which is a tetramer having two subunits of each enzyme. The anthranilate synthase catalyzes reaction (7) and the phos-phoribosyltransferase catalyzes two reactions the N-terminal portion cleaves glutamine to glutamate giving NH3 for the anthranilate synthase, while the C-terminal portion catalyzes reaction (8).3,1,312 All these reactions require M2+ cations. Orotate phosphoribosyltransferase binds four Mn2+ ions in a cooperative fashion kinetic data have been interpreted in a scheme where both metal-free and metal-containing enzyme catalyze the reaction.313... 

Anthranilate synthase-phosphoribosyltransferase Salmonella typhimurium, 582 Anthranilic acid synthe,sis... 

This enzyme [EC 4.1.3.27] catalyzes the reaction of chorismate with glutamine to generate anthranilate, pyruvate, and glutamate. 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 (Le., indole-3-glycerol-phosphate synthase, anthranilate phosphoribosyltransferase, tryptophan synthase, and phosphoribosylanthranilate isomerase). The anthranilate synthase that is present in these complexes has been reported to be able to utilize either glutamine or ammonia as the nitrogen source. However, it has also been reported that when anthranilate synthase is separated from this complex, only ammonia can serve as a substrate. 

T) anthranilate synthase ( anthranilate phosphoribosyltransferase ( 7V-(5 -phosphoribosyl)-anthranilate isomerase indole-3-glycerol phosphate synthase tryptophan synthase... 

Scheme 12.24. Chorismate is converted to anthranilate (and glutamate [Gin, E] and pyruvate) using anthranilate synthase (EC 4.1.3.27). Anthranilate and ribose-1,5-diphosphate, in the presence of anthranilate phosphoribosyltransferase (EC 2.4.2.18), produces N- 5-phospho-P-D-ribosyl) anthranilate. Finally, indole-3-glycerolphosphate is formed via l-(2-carboxyphenyl-amino)-l-deoxy-D-ribulose-5-phosphate with loss of carbon dioxide (CO2).

Anthranilate phosphoribosyltransferase 2 phosphoribosyl anthranilate isomerase 3 indole-3-glycerol phosphate synthase 4 tryptophan synthase 25 Luckner, Metabolism... 

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