Comparative tyrosine degradation in Vibrio cholerae strains. The strain ATCC 14035 as a prokaryotic melanogenic model of homogentisate-releasing cell.
The relationship between L-tyrosine catabolism and melanin formation was studied in the Vibrio cholerae strains ATCC 14035 and CECT 557. It is shown that both strains degrade L-tyrosine by the same pathway as eukaryotic cells, giving homogentisate as intermediate. ATCC 14035, an O1 strain, which is not able to grow using L-tyrosine as sole carbon and energy source, but it forms pyomelanin from homogentisate. The second strain, which is non-O1, is able to grow using L-tyrosine as sole carbon and energy source, but it does not form any pigment. Both strains contain all the enzymes involved in the L-tyrosine catabolism. The three late enzymes of the pathway, homogentisate oxygenase, maleylacetoacetate isomerase and fumarylacetoacetate hydrolase, are induced by L-tyrosine, but the degree of induction is much lower in the ATCC 14035 strain. Thus, the distal part of the pathway becomes the rate-limiting steps in the L-tyrosine catabolism, explaining homogentisate accumulation and pyomelanogenesis in this strain. It is proposed that V. cholerae might be a useful prokaryotic model to show that alkaptonuria and other diseases related to L-tyrosine metabolism could occur in animals even when no particular enzyme involved in that pathway is lacking.
Sanchez-Amat
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A
Department of Genetics and Microbiology, Faculty of Biology School of Medicine, University of Murcia, Spain.
Ruzafa
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C
Solano
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F
D049308:Dioxygenases; D004790:Enzyme Induction; D050560:Homogentisate 1,2-Dioxygenase; D006713:Homogentisic Acid / Q000378:metabolism; D006867:Hydrolases / Q000096:biosynthesis / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D010105:Oxygenases / Q000096:biosynthesis / Q000378:metabolism; D012703:Serotyping; D014443:Tyrosine / Q000378:metabolism*; D014734:Vibrio cholerae / Q000145:classification* / Q000254:growth & development / Q000378:metabolism*; D019745:cis-trans-Isomerases / Q000096:biosynthesis / Q000378:metabolism
D014443:Tyrosine; D010105:Oxygenases; D049308:Dioxygenases; D050560:Homogentisate 1,2-Dioxygenase; D006867:Hydrolases; C020156:fumarylacetoacetase; D019745:cis-trans-Isomerases; C021531:maleylacetoacetate isomerase; D006713:Homogentisic Acid