Histidine ammonia lyase (HAL) isolated from Corynebacteriaceae can decrease serum histidine levels, induce accumulation of urocanic acid, and is not inhibited by L-histidinol. As a result, histidine ammonia lyases similar to the one isolated from Corynebacteriaceae are uniquely suitable for combination...http://www.google.de/patents/US6939541?utm_source=gb-gplus-sharePatent US6939541 - Cloning, overexpression and therapeutic use of bioactive histidine ammonia lyase
