Myrosinase

Myrosinase (or thioglucoside glucohydrolase) is a family of enzymes involved in plant defense against herbivores. Their structure has been elucidated and is available.^[1]

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Myronsinase activity

Myrosinase is regarded as a defense-related enzyme and is capable of hydrolyzing glucosinolates into various compounds, some of which are toxic.^[2]

In the presence of water, myrosinase cleaves off the glucose group from a glucosinolate. The remaining molecule then quickly converts to a thiocyanate, an isothiocyanate or a nitrile; these are the active substances that serve as defense for the plant.

The glucosinolate-myrosinase defensive system is packaged in the plant in a unique manner. The degradative myrosinase enzymes, which catalyze the hydrolysis of glucosinolate molecules, are largely stored within myrosin grains in myrosin cells, but have also been reported in protein bodies/vacuoles, and as cytosolic enzymes which tend to bind to membranes (Luthy and Matile 1984). When the mechanism isolating the two compounds breaks down, such as by the destruction of plant matter by an herbivore, the myrosinase hydrolization of available glucosinolate substrate occurs.

References

Luthy B, Matile P. The mustard oil bomb - rectified analysis of the subcellular organization of the myrosinase system. Biochem Physiol Pfl 179 (1-2): 5-12 (1984).