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PubMedDate not supplied

[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. Free amino acids however are competitive inhibitors and in the majority of cases exchange alpha-proton. The presence of COOH-group is therefore an important feature which determines the binding efficiency and causes the "active" conformation of the amino acid-PLP complex labelising alpha-proton. In the absence of functional and bulky groups in the amino acid side chain the hydrophobicity is found to be the main factor determining the binding efficiency. For these amino acids a correlation exists between-RTlnKi and side chain hydrophobicity. The amino acids bearing the bulky groups, i. e. valine, leucine and isoleucine have reduced binding efficiency. Lysine and arginine bearing positively charged functional groups possess no inhibition effect. Aspartic and glutamic acids are anomalously strong inhibitors taking into consideration low hydrophobicity of their side chains. One can assume that the electrophilic group able to interact with the terminal COO- -group of aspartic and glutamic acids is located in the active site of tyrosine phenollyase.

Amino Acids↗
PubMedDate not supplied

[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. Monovalent cations affect the absorption and CD spectra of the enzyme and its complex with the quasi-substrate--L-alanine. It was suggested that an activation of tyrosine phenollyase by monovalent cations was connected with the increase of the active protonated form of the holoenzyme (lambda max 420 mm) induced by the cations-activators.

Catalysis↗
PubMed1981

[Influence of chloramphenicol on glutamic acid excretion in citrobacter intermedius C3 (author's transl)].

Chloramphenicol inhibits growth of C. intermedius C3 along with glutamic acid excretion, isocitrate dehydrogenase, glutamate dehydrogenase and the percentage of glutamic acid excreting colonies in solid medium. Repression of isocitrate dehydrogenase and glutamate dehydrogenase may explain the observed decrease in extracellular glutamic acid accumulation even when media were supplemented with 2-oxoglutarate, a known inducer of excretion in C. intermedius C3.

Cell Division↗