Kamel, M. Y., and S. A. Maksoud, "Co-Factor Requirements and Factors Affecting L-Histidine Ammonia-Lease Activity in Vicia faba", Zeitschrift für Pflanzenphysiologie, vol. 88, no. 3, pp. 255-262, 1978. AbstractWebsite

Summary In the present work, an assay for L-histidine ammonia lyase (L-HAL) from Vicia faba isdescribed. The necessity of divalent metal ion, -SH reagent, cyano-combalamine (B12) and AMP for optimal enzyme activity were investigated. The changes in the concentration of total free α-amino acids and histidine were determined for various stages of growth of two types of Vicia faba (Romi and Baldi). It was found that the concentration of histidine in the two types reached a maximum value on the 11th and the 9th day, respectively, and coincided with the maximum in vivo level of L-HAL. This finding suggests that Vicia faba L-HAL is an iducible enzyme which is metabolically regulated via changes in the cell-free histidine concentration.

Maksoud, S. A., H. A. Hosni, and H. El-Badawi, Distribution of urease in the seeds of some Egyptian species of Malvaceae and Tiliaceae., , vol. 21, pp. 209–217, 1997. Abstract
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Kamel, M. Y., S. A. Maksoud, and E. H. A. Youssef, "Non-oxidative Deamination of Histidine to Imidazole Propionic Acid by an Enzyme Preparation from Vicia faba", Zeitschrift für Pflanzenphysiologie, vol. 92, no. 3, pp. 255-261, 1979. AbstractWebsite

Summary A method for the preparation of a 50 fold purified enzyme from Vicia faba catalyzing the non-oxidative deamination of histidine to imidazole propionic acid and ammonia is described. AMP and B12 requirement for the purified enzyme is indicated. The enzyme exhibited optimal activity at pH 9.0 in pyrophosphate buffer. Km values for L-histidine, AMP and B12 were found to be 4.0 mM, 6.2 mM and 0.97 mM, respectively. Chromatographic analysis and the stoichiometric relationship between enzymatically liberated ammonia and product formed suggested that the enzymatic product is imidazole propionic acid.