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

Myrosinase activity

Myrosinase is regarded as a defence-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 [3]. 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.


  1. ^ Myrosinase structure
  2. ^ A wound- and methyl jasmonate-inducible transcript coding for a myrosinase-associated protein with similarities to an early nodulin
  3. ^ 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).