35 . The Tryptophanase - tryptophan Reaction
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چکیده
The facts described by Happold &'Hoyle [1936] and Evans et al. [1941] can be concisely stated as follows: (1) In a complex medium (e.g. bouillon, casein-digest, etc.) in which the presence of glucose in sufficient amount inhibits completely the production of indole by B. coli, the complete tryptophanase system is absent from the cells. (2) With a simple salt medium as used by Fildes, glucose only partly inhibits the production of indole (up to about 80 %), but such inhibition can be completed by the additiQn of either phenylalanine or tyrosine in certain stoichiometrical relationships to the tryptophan present. This completion of the inhibition by these amino-acids is specific. The problem therefore resolves itself into two questions, (a) the actual mechanism of the glucose inhibition, and (b) the part played by these specific amino-acids. We have attempted to throw some light upon the glucose inhibition by using either: (a) Complex media like bouillon or a casein-digest medium where the necessary amino-acids are present in ample quantity. (b) Fildes synthetic medium together with the addition of the requisite amount of phenylalanine or tyrosine.
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Reaction pathway of tryptophanase-catalyzed L-tryptophan synthesis from D-serine.
Tryptophanase, L-tryptophan indole-lyase with extremely absolute stereospecificity, can change the stereospecificity in concentrated diammonium hydrogenphosphate solution. While tryptophanase is not inert to D-serine in the absence of diammonium hydrogenphosphate, it can undergo L-tryptophan synthesis from D-serine along with indole in the presence of it. It has been well known that tryptophana...
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