Syntheses of l-Tyrosine-Related Amino Acids by Tyrosine Phenol-lyase of Citrobacter intermedius

Degradation of tyrosine to phenol, pyruvate and ammonia by tyrosine phenol-lyase from Citrobacter intermedius (formerly named Escherichia intermedia) is readily reversible at high concentrations of pyruvate and ammonia. Spectrophotometric studies indicate that ammonia is the first substrate which interacts with bound pyridoxal 5′-phosphate. Kinetic results show that pyruvate is the second substrate bound, hence phenol must be the third. When an appropriate phenol derivative is substituted for phenol, the corresponding tyrosine analogue can be synthesized. 3-Fluoro-, 2-fluoro-, 3-chloro-, 2-chloro-, 3-bromo-, 2-bromo-, 2-iodo-, 3-methyl-, 2-methyl and 2-methoxy-l-tyrosines have been synthesized by this reaction. By using various phenol derivatives or tyrosine analogues as substrates, the substrate specificity of tyrosine phenol-lyase is investigated, and the situation of its active site is discussed.