This enzyme, which has been found in all species and tissues examined, catalyses the hydrolytic deamination of imine intermediates formed by several types of pyridoxal-5'-phosphate-dependent dehydratases, such as EC
4.3.1.19, threonine ammonia-lyase and EC
4.3.1.17, L-serine ammonia-lyase. The reactions, which can occur spontaneously, are accelerated to minimize the cellular damage that could be caused by these reactive intermediates.