Definition of Argininosuccinate lyase

ASL (argininosuccinate lyase) is a human gene that makes the protein argininosuccinate lyase, one of the enzymes controlling a series of reactions called the urea cycle. The ASL enzyme starts the reaction in which the amino acid arginine, a building block of proteins, is produced from argininosuccinate:

The urea cycle is a sequence of reactions in the cells of the liver. It processes excess nitrogen, generated when protein is used by the body, to make a compound called urea that is excreted by the kidneys. Eliminating the excess nitrogen in this way prevents it from accumulating in the form of ammonia, which is toxic.