Blue-Green Bacteria synthesise L-Tyrosine by the Pretyrosine Pathway

THE similarity of major biochemical pathways throughout the animal and plant kingdoms1 presumably reflects the ancient formation of the pathways in a common ancestral counterpart of modern cell types. The pathway previously known for L-tyrosine biosynthesis in both prokaryotie and eukaryotic microorganisms (Fig. 1a) involves a dehydrogenation-decarboxylation conversion of prephenate to 4-hydroxyphenylpyruvate followed by transamination in the presence of a suitable amino donor. Our data (Fig. 1b) demonstrate a reversed order of these two reactions in several species of blue–green algae (more appropriately designated bacteria (order Chrooeocales2)).