An Auxin Inactivation System Involving Tyrosinase

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Abstract
Indoleacetic acid (IAA) is inactivated by mushroom tyrosinase or a tyrosinase present in dialyzed extracts of growing leaves of the fern Osmunda cinnamomea, but only in the presence of certain phenols, such as catechol or pyrogallol. Tyrosine and 3,4-dihydroxyphenylalanine do not promote IAA inactivation althpugh these phenols are oxidized by the enzyme. It appears probable that a reaction occurs between IAA and one of the intermediate compounds formed during the oxidation of catechol or pyrogallol. Possible mechanisms for the reaction, as well as its implications for auxin destruction in plant extracts are discussed.
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