OMR1 (L-O-METHYLTHREONINE RESISTANT 1); L-threonine ammonia-lyase; first enzyme in the biosynthetic pathway of isoleucine ; Catalyzes the formation of alpha-ketobutyrate from threonine in a two-step reaction. The first step is a dehydration of threonine, followed by rehydration and liberation of ammonia (592 aa)