Synthesis of l-tyrosine from phenol and S-(o-nitrophenyl)-l-cysteine catalysed by tyrosine phenol-lyase

The enzymatic synthesis of amino acids has attracted considerable biotechnological interest in recent years. We have investigated the use of tyrosine phenol-lyase from Citrobacter freundii (ATCC 29063) in the synthesis of l -tyrosine from a high Vmax, low Km substrate, S -(o- nitrophenyl)- l -cysteine , and phenol. Reactions with soluble S -(o- nitrophenyl)- l -cysteine are rapid, reaching completion in 2 h or less, and resulting in approximately 70% conversion of phenol to l -tyrosine without large excesses of reactants. The pH optimum of this reaction is broad, extending from pH 6.8 to above 9. Since S -(o- nitrophenyl)- l -cysteine is readily prepared from l -cysteine and o-fluoronitrobenzene, this reaction is potentially valuable for the synthesis of l -tyrosine and analogues.