Pathways of Phenylalanine and Tyrosine Metabolism Utilized Principally by Microorganisms

Pathways of Phenylalanine and Tyrosine Metabolism Utilized Principally by Microorganisms 

Baumann (36, 38) suggested the following scheme for tyrosine degradation by the bacterial flora of the gut  

These substances are all excreted in normal human urine (535) and are thought probably to arise from bacterial action, but not all the transformations postulated by Baumann are probable. For example, as we shall see below, phenol is formed directly from tjirosine. Though benzoic and p-hydroxybenzoic acids can be formed from phenylalanine and tyrosine, for example, by Pseudomonas species (346, 833), a plant rather than bacterial origin has been suggested for the benzoic acid moiety of the hippuric acid excreted by man (59). 

Recent work suggests that benzoic acid can be formed in mammalian tissues (330a, 776a). 

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