Myrosinase-associated proteins

TAIPALENSUU, J., ANDREASSON, E ERIKSSON, S., RASK, L Regulation of the wound-induced myrosinase-associated protein transcript in Brassica napus plants., Eur. J. Biochem., 1997,247,963-971. 

Taipalensuu, J., Falk, A. and Rask, L. (1996) A wound-and methyl jasmonate-inducible transcript coding for a myrosinase-associated protein with similarities to an early nodulin. Plant Physiol, 110, 483-91. 

A major proportion of the glucosinolate hydrolysis products formed upon myrosinase cleavage in some plants are nitriles. In vitro, nitrile formation associated with myrosinase-catalyzed hydrolysis is enhanced at low pH (pH<3) and in the presence of ferrous ions. In vivo, protein factors in addition to myrosinase may be responsible for nitrile formation. If the glucosinolate side chain has a terminal double bond, the sulfur released from the thioglucosidic bond may be captured by the double bond and an epithionitrile is formed.9 This reaction takes place only in plants that possess a protein factor known as epithiospecifier protein (ESP). ESP activities have been identified in several species of the Brassicaceae and shown to influence the outcome of the myrosinase-catalvzed hydrolysis reaction although they have no hydrolytic activity by themselves.10 12 The mechanism by which ESPs promote epithionitrile formation is not known. 

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