Histidine by Bacterial Enzymes

The correct catabolic pattern of histidine was established first in bacterial preparations and for this reason will be discussed first. Cell-free extracts of Pseudomonas fluorescens were obtained which catalyze the quantitative conversion of L-histidine to L-glutamic acid, formic acid, and 2 moles of NH3, as required by equation 14. Proof of the formation of L-glutamate was obtained by isolating the crystalline hydrochloride from the incubation mixture and establishing its identity.  

Additional indirect evidence that this carbon yields formate or some other 1-carbon unit is that administration of histidine labeled in the 2-position to rats resulted in considerable amounts of activity in 

The results of the experiments with the variously labeled histidines lead to the scheme of catabolism shown in Fig. 14. 

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