Other Catabolic Pathways in Bacteria

The observations that have been made permit the construction of a broad conceptual scheme that describes the oxidation of tryptophan by many bacteria, and that links up one of the possible alternate pathways for the metabolism of tryptophan with a series of other primary oxidative sequences previously known to occur in bacteria. 

Histidine is of interest biologically for a variety of reasons in addition to the fact that it is a naturally occurring amino acid. In the young rat 

Parke and Williams,210 however, point out that the cis, irans-muconic acid is readily transformed to the cis, cis form on crystallization from water, and, therefore, they consider that it is probable that the cis, irons-muconic acid is actually the true product. This is difficult to understand in view of the inactivity of the cis, trans acid.  

Structural formulas of these compounds are shown below  

The presence of similar structural groups in their molecules led to much speculation and experimental work to demonstrate whether histidine could serve as a precursor for the synthesis of arginine, creatine, the purines, and the pyrimidines. These deductions have all been shown to be erroneous in the course of time. 

---