Wiktionary
n. (context enzyme English) Any of several defense-related enzymes, in plants such as mustard, that hydrolyze glycosides thus releasing potentially toxic substances
Wikipedia
Myrosinase (, thioglucoside glucohydrolase, sinigrinase, and sinigrase) is a family of enzymes involved in plant defense against herbivores. The three-dimensional structure has been elucidated and is available in the PDB (see links in the infobox).
A member of the glycoside hydrolase family, myrosinase possesses several similarities with the more ubiquitous O- glycosidases. However, myrosinase is the only known enzyme found in nature that can cleave a thio-linked glucose. Its known biological function is to catalyze the hydrolysis of a class of compounds called glucosinolates.