[The degradation of tryptophan in Endomycopsis Vernalis and other yeasts]

Abstract

1. The degradation of tryptophan (Try) and some of its potential intermediates has been studied in Endomycopsis vernalis. The following degradation products were identified in surface-cultures of Endomycopsis which had been fed with C-14-labeled D,L-Try for 12-24 hrs: β-(indolyl-3)-pyruvic acid (IBS); β-(indolyl-3-)lactic acid (IMS); α-(indolyl-3-)acetic acid (IES); indolyl-3-carboxylic acid (ICS); β-(indolyl-3-)ethanol (β-IÄ); indole-3-aldehyde (IAld); Nα-acetyl-tryptophan (Ac-Try). Indole-3-acetaldehyde (IAAld) could be demonstrated only in experiments in which cell-free extracts were used. 2. IMS was isolated from the culture medium and was identified by means of chemical methods and IR- and mass-spectra. Feeding of both D- and L-Try yielded L-(-)-indolyllactic acid exclusively. 3. The first step in the breakdown of Try has been shown to be a transamination-reaction leading to the formation of IBS. The NH2-group can be transferred to α-ketoglutaric acid as well as to phenylpyruvic acid. 4. The degradation products of Try were determined quantitatively by feeding C-14-(3-alanyl-) D,L-Try to Endomycopsis cultures. After 10 hrs nearly 60% of the original radioactivity of Try was found in IMS. In comparison to IMS the concentrations of the other degradation products formed were rather small: Ac-Try (about 1/7 of the IMS-concentration), IES (1/10), β-IÄ (1/12), ICS (1/80), IAld (1/220). 5. The following pathways in the degradation of Try in Endomycopsis vernalis are assumed to be of physiological, i.e., enzymatic, nature: Try→IBS→IAAld→β-IÄ, and Try→Ac-Try, and IBS→IMS. IMS and β-IÄ appear to be metabolic end products.