title: Characterization of the melanogenic system in Vibrio cholerae, ATCC 14035.
abstract: The nature of the pigment formed by Vibrio cholerae and 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 cholerae contained transaminases that transforms L-tyrosine into p-hydroxyphenylpyruvate. Moreover, Vibrio cholerae is 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 by Vibrio cholerae is 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 all these pigments.
authors.affiliation: Department of Biochemistry, Molecular Biology B, Faculty of Biology, University of Murcia, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Ruzafa
authors.forename: A
authors.initials: A
authors.lastname: Sanchez-Amat
authors.forename: F
authors.initials: F
authors.lastname: Solano
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D006713:Homogentisic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008543:Melanins / Q000096:biosynthesis*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010667:Phenylpyruvic Acids / Q000378:metabolism; D000637:Transaminases / Q000378:metabolism; D014443:Tyrosine; D014734:Vibrio cholerae / Q000378:metabolism*
chemical_list: D003470:Culture Media; D008543:Melanins; D010667:Phenylpyruvic Acids; C010590:4-hydroxyphenylpyruvic acid; D014443:Tyrosine; D014442:Monophenol Monooxygenase; D000637:Transaminases; D006713:Homogentisic Acid