Arogenate (pretyrosine) as an obligatory intermediate of the biosynthesis of l-tyrosine in chloridazon-degrading bacteria

Abstract

The biosynthesis of the aromatic amino acids L-phenylalanine and c-tyrosine in microorganisms is extensively studied [1-3]. The textbook route utilizes the intermediates phenylpyruvate for phenylalanine and 4-hydroxyphenylpyruvate for tyrosine biosynthesis. Cyanobacteria were the first group of prokaryotes shown to depend upon a different sequence requiring arogenate as a tyrosine precursor [4]. Subsequently, the obligatory use of the arogenate for tyrosine biosynthesis in coryneform bacteria [5] and the yeast Hansenula henricii [6], and the dual enzyme sequences to tyrosine via 4 -hydroxyphenylpyruva te and arogenate in Pseudomonas aeruginosa [7] were demonstrated. Studying the biosynthesis of phenylalanine and tyrosine in chloridazon-degrading bacteria which are able to grow on the synthetic compound chloridazon (5 amino 4 chloro2 phenyl3(2H)pyridazinone, the active ingredient of the herbicide Pyramin ~) as sole carbon source, only a petty prephenate dehydrogenase activity could be detected [8]. The taxonomic classification of the chloridazon-degrading bacteria is very difficult, and they could not be unequivocally classified according to Bergey's Manual [9]. This paper concerns the evidence of the arogenate dehydrogenase in chloridazon-degrading bacteria, and we discuss the approach to confine the relatedness of this bacterium to other groups of bacteria by an enzymological patterning.