[Interaction of tyrosine-phenol-lyase from Citrobacter intermedius with amino acids and their derivatives: factors determining the effectiveness of binding].

The inhibition by L-amino acids and their derivatives of tyrosine phenol-lyase is investigated. Tyramine, alpha-phenylethylamine and tryptamine have no detectable inhibition effect and hence are weakly bonded by an active site. The aromatic amino acid amides are competitive inhibitors but do not manifest an enzymatic isotope exchange of alpha-proton in D2O.

[Substrate specificity of tyrosine-phenol-lyase. Electron and steric control at the stage of aromatic moiety elimination].

We have investigated the electronic and steric effects of substituents in the aromatic moiety of the substrate on the two principal stages of the reaction catalyzed by tyrosine-phenol-lyase. The substrate specificity of the enzyme is controlled during the stage of elimination of the aromatic ring. The process may be formally considered as an electrophilic substitution in the aromatic nucleus and includes tautomerization of the phenol group into cyclohexadienone and subsequent beta-elimination with regeneration of aromaticity in the leaving group.

[Effect of monovalent cations on the catalytic and spectral properties of tyrosine-phenol-lyase from Citrobacter intermedius].

The action of monovalent cations Li+, Na+, K+, Rb+, Cs+, NH4+ on catalytic and physico-chemical properties of bacterial tyrosine--phenol-lyase was investigated. It was shown that K+, Rb+, Cs+, NH4+ were the noncompetitive activators of the enzyme, Na+ was an inhibitor, Li+ did not influence the catalytic activity. The values of KA and Vmax were determined for the activators in the reaction of alpha, beta-elimination of L-tyrosine.

[Isolation and properties of tyrosine phenol-lyase from Citrobacter intermedius].

A method for preparation of homogeneous tyrosine phenol lyase (EC 4.199.2) from Citrobacter intermedius has been developed.