The protein encoded by the Shewanella colwelliana melA gene is a p-hydroxyphenylpyruvate dioxygenase

The identity of the product of the melA gene from Shewanella colelliana with the enzyme p-hydroxyphenylpyruvic dioxygenase is shown. Cloning of the melA gene endowed Escherichia coli with the capacity to synthesize melanin-like pigments from L-tyrosine. E. coli contained transaminases that transforms L-tyrosine into p-hydroxyphenylpyruvate. This keto acid was detected in the cultures. On the other hand, E. coli containing melA was able to go further in the catabolic pathway, releasing a great amount of homogentisic acid. This acid can spontaneously polymerize giving the pigment. Furthermore, p-hydroxyphenylpyruvate dioxygenase activity was detected in this system. Analysis of the deduced amino acid sequence revealed a high homology with the p-hydroxyphenylpyruvate deoxygenase enzyme from different organisms.