When the freshly drawn juices of certain plants are allowed to stand for a short time exposed to air their color turns to an intense black. It is by such a process as this that the lacquers used in oriental countries are produced. Bertrand found a few years ago that this change in color is due to the action of an oxidizing ferment, laccase, upon a substance that is oxidized with great readiness, laccol, and which is chemically a member of the aromatic series. Laccase has since been shown capable of oxidizing many other aromatic substances. Similar oxidizing ferments seem to be present in many and varied forms of plants, among them the mushrooms. In mushrooms Bertrand found, besides a ferment resembling laccase, one whose oxidizing power was limited to a specific action on tyrosin, and therefore called tyrosinase. Beet roots and the dahlia also contain tyrosinase.
Otto v. Fürth
TYROSINASE, A FERMENT PRODUCING A PIGMENT RESEMBLING MELANIN. JAMA. 1901;XXXVII(24):1612. doi:10.1001/jama.1901.02470500040006
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