The enzyme 5-guanidino-2-oxopentanoate decarboxylase () catalyzes the chemical reaction
This enzyme belongs to the family of lyases, specifically the carboxy-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 5-guanidino-2-oxo-pentanoate carboxy-lyase (4-guanidinobutanal-forming). Other names in common use include alpha-ketoarginine decarboxylase, and 2-oxo-5-guanidinopentanoate carboxy-lyase. It has 2 cofactors: thiamin diphosphate, and Divalent cation.