Chorismate bacillus subtilis

Kast P, M Asif-Ullah, D Hilvert (1996) Is chorismate mutase a prototypic entropy trap Activation parameters for die Bacillus subtilis enzyme. Tetrahedron Lett. 37 (16) 2691—2694... 

No reports have appeared on the detection in plants of chorismate synthase the flnal enzyme in the prechorismate portion of the shikimate pathway. The enzyme has been purified to apparent homogeneity from Bacillus subtilis (Hasan and Nester, 1978). 

Chook, Y.M., Ke, H. and Lipscomb, W.N. (1993) Crystal Structures of the Monofunctional Chorismate Mutase from Bacillus subtilis and its Complex with a Transition State Analog, Proc. Nat. Acad. Sci. USA, 90, 8600-8603. 

Why is 1F7 10 -times iess active than chorismate mutase The antibody molecule s distinctive architecture does not appear to impose intrinsic structural limitations on catalysis. Indeed, comparison of the active sites of the antibody and the monofunctional enzyme from Bacillus subtilis [26] suggests that the differences between them are more a matter of degree than of kind. Upon complex formation, the hapten is buried to a similar extent in both proteins, and similar types of interactions are available for orienting the flexible substrate correctly for reaction. Furthermore, the enzyme and the antibody seem to promote the rearrangement of chorismate via the same concerted transition state as the uncatalyzed reaction. Other formal mechanistic possibilities, such as a two-step heterolytic process assisted by an enzymic nucleophile, can be ruled out by the lack of appropriate functional groups in the respective active sites [25,26]. 

The elucidation of the steps in the common part of the pathway from carbohydrate precursors to the formation of chorismate remains a classic example of the combined use of auxotrophic mutants, isotop-ically labelled precursors and finally enzyme studies to define a metabolic sequence. An auxotrophic mutant of an organism is a nutritional mutant. The genetic change in such mutant strains causes an inability to carry out one of the reactions in a biosynthetic pathway leading to one or more essential metabolites. Analysis of the sequence of steps in the biosynthetic pathway is facilitated by the fact that each mutant may accumulate in its culture fiuid the substrate for the enzymic reaction which is blocked and may utilise later members of the sequence to replace the required metabolites Davis S produced auxotrophic mutants of Escherichia coli, Aerobacter aerogenes. Bacillus subtilis and Salmonella typhitnurium by ultra-violet irradiation of a bacterial culture in a minimal medium of salts plus D-glucose. Selection of the mutant strains was dependent on the use of the observation that penicillin kills bacterial cells only... 

End-product inhibition of AS activity by tryptophan appears to be a rather common control mechanism among microorganisms. Nester and Jensen [71] described tryptophan inhibition of B. subtilis AS activity as the first step in sequential feedback control. Excess tryptophan would result in inhibition of the conversion of chorismate to anthrani-late. The consequent accumulation of chorismic acid would then serve as a feedback inhibitor of the DAMPS, the first enzyme in the pathway leading to chorismate synthesis. Bacillus alvei has an anthranilate synthetase which is extremely sensitive to inhibition by tryptophan [98]. In contrast to the mode of AS feedback inhibition in E. coli and S. typhimurium, the B. alvei AS is inhibited by tryptophan noncom-petitively with respect to chorismate and uncompetitively with respect to glutamine. It is the only Bacillus species, among 21 studied, which did not exhibit a sequential feedback control pattern [79]. 

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