Tryptophan Metabolites: A Microbial Perspective

Abstract

The discovery of the regulation of tryptophan biosynthetic pathway by means of a repressible operon has been recognised as a milestone in genetics. This long multistep pathway is energetically so expensive that numerous allosteric control loops exist in addition to tight genetic regulation. That's why essential amino acid tryptophan is a valuable product for food industry and animal breeding. Traditionally, vitamin auxotrophs of soil microorganisms have been used for amino acid manufacturing. However, in the age of synthetic biology, metabolic engineering has recently become the method of choice to construct the producer strains.Additionally, in contrast to mammalian cells, bacterial cells are able to produce tryptophan starting at central metabolic intermediates from pentose phosphate pathway and glycolysis. This metabolic divergence provides an excellent target for the development of novel antimicrobials which interfere with the biosynthesis of tryptophan.Tryptophan metabolism makes at least two contributions to microbial quorumsensing pathways, which may have implications in antimicrobial chemotherapy. The autoinducers of renowned Pseudomonas quinolone signalling system originate either from kynurenine or shikimate pathways. Fluorinated 4-quinolone derivative antimicrobial drugs exhibit antipathogenic effects at subinhibitory concentration, presumably by interfering with Pseudomonas quinolone signalling. Another recently recognised bacterial signal molecule is indole, a degradation product of tryptophan. Unconventional stationary phase signal molecule indole is unique, as no receptor/response regulator protein has been identifi ed to date. Instead, the effects of indole have been attributed to its physicochemical interaction with the cell membrane.

Variation of Volatile Compounds and Corresponding Aroma Profiles in Chinese Steamed Bread by Various Yeast Species Fermented at Different Times

“…Indole is a degradation product of tryptophan through the action of tryptophanase. 34 Further Confirmation of Key Aroma Compounds in CSBs by Odor Activity Values. As the concentration of hexanol, 3-ethoxy-1-propanol, 1-octen-3-ol, 1-octen-3-one, methional, and 3-methylthiopropanol was too low to be detected by GC−MS, the remaining 35 compounds were quantified.…”

“…The FD value of indole in the steamed bread samples was not high, and it had a positive contribution to the aroma of steamed bread. Indole is a degradation product of tryptophan through the action of tryptophanase …”

Characterization of Aroma-Active Compounds in Four Yeast Extracts Using Instrumental and Sensory Techniques

“…Four YE samples, which had an identical animal note with high scores (Table ), had the same aroma-active compound indole with a content ranging from 2.5 to 176 mg/kg. Indole is a degradation product of tryptophan through the action of tryptophanase. , On the other hand, styrene expressed an FD factor of 32 both in FA31 and KA02 powder but an FD factor of 8 in LA00L paste. 2-Acetylpyrrole showed high FD factors (from 32 to 512) in four YE samples with a musty, nutty, and coumarinic odor.…”

The association between dietary amino acid profile and the risk of type 2 diabetes: Ravansar non-communicable disease cohort study

“…Tryptophan is involved in the tryptophan-kynurenine and tryptophan-methoxy indole metabolic pathways, which leads to the production of some active metabolites, including kynurenine, kynurenic acid, and serotonin [43]. Any disturbance in these metabolic pathways is likely to be associated with the development of T2D [44].…”