8o. THE COLI-TRYPTOPHAN-INDOLE REACTION 3. ESSENTIAL STRUCTURAL CONDITIONS FOR THE ENZYMIC DEGRADATION OF TRYPTOPHAN TO INDOLE BY JOHN WILLIAM BAKER AND FRANK CHARLES HAPPOLD

THE reaction whereby l-tryptophan is broken down to indole by E. coli has been studied independently by Woods [1935, 1, 2] and by Happold & Hoyle [1935]. Woods worked with washed viable cells of the organism, whereas the latter investigators used suspensions killed in various ways but which, nevertheless, retained the property of catalysing this reaction. By coincidence both investigations, although following different courses, included examination of a similar selection of those indole derivatives which, on the basis of various mechanisms suggested in the literature, should be intermediate stages in the breakdown. Both sets of data (obtained by different techniques) uniformly revealed failure to produce indole from such derivatives and thus effectively disproved the validity of current mechanisms which, after all, had been formulated solely on analogy to other degradations. Woods [1935, 2] also studied the kinetics of the reaction and showed that the process requires 5 atoms of oxygen, that the conversion of tryptophan into indole goes to completion, and that the rate of indole production is equal to the rate at which the tryptophan disappears. The reaction could be represented