Dual enzymatic routes to L-tyrosine and L-phenylalanine via pretyrosine in Pseudomonas aeruginosa.

Pretyrosine, an intermediate of L-tyrosine biosynthesis in blue-green algae, was found to be enzymatically formed and utilized in Pseudomonas aeruginosa. The enzymology and regulation of aromatic biosynthesis were re-evaluated in the context of these new findings, Four species of aromatic aminotranaferase were separated and partially purified. Each was reactive with prephenate, phenylpyruvate, and 4-hydroxyphenylpyruvate. Molecular weights of aminotransferases L)E I and HA I were 70,000, whereas aminotransferases HA II and HA III had molecular weights of 200,000. L-Glutamate was the best amino donor reactant with aminotransferase DE I, whereas I.-leucine was best with the remaining three aminotransferases. Gel filtration, DEAE-cellulose chromatography, and hydroxylapatite chromatography did not separate prephenate