The nature of the pigment formed byVibrio choleraeand the characterization of its biosynthetic pathway is shown. This microorganism is able to synthesize melanin‐like pigment when cultured in the presence of L‐tyrosine. Other phenolic chemicals related to L‐tyrosine do not lead to pigment production. The microorganism has no tyrosine hydroxylase activity, and the levels of dopa oxidase activity are very low, making the existence of a tyrosinase very unlikely. However,Vibrio choleraecontained transami‐nases that transforms L‐tyrosine into p‐hydroxyphenylpyruvate. Moreover,Vibrio choleraeis able to go further in the catabolic pathway, releasing a great amount of homogentisic acid. This acid can spontaneously be oxidized to its p‐quinone form, which subsequently polymerizes leading to pigment formation. It is concluded that the pigment formed byVibrio choleraeis not synthesized by the Raper‐Mason pathway, but by a L‐tyrosine catabolism pathway leading to homogentisic acid. Some simple properties of that melanin are compared to model eu‐ and pheomelanin, but no clear distinction could be stated, indicating the similarity between
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