Presence of -SH groups in liver tissue arginase of sheep, and the effects of amino acids containing sulfur, aromatic and hydroxylic amino acids on enzyme activity

Benzer, F.; Ozan, S.T.

Saglk Bilimleri Dergisi, Firat Universitesi Veteriner 16(1): 65-70


Accession: 003894339

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The effects of tyrosine and tryptophan from aromatic amino acids, serine and threonine from hydroxylic amino acids, cysteine and methionine from amino acids having a sulfur group, and homocysteine from amino acids that do not occur in proteins on arginase in sheep liver tissue were investigated. The study also determined whether there are thiol groups in the enzyme structure, and assessed the effects of p-chloromercuri benzoate and n-ethylmaleimide. Arginase was found to be inhibited by cysteine, homocysteine and tryptophan, but was less activated by serine and threonine. Methionine and tyrosine did not affect arginase activity. While p-chloromercuri benzoate, cysteine and homocysteine activated arginase at low concentrations, they inhibited enzyme activity at high concentrations. Cysteine, homocysteine and tryptophan from amino acids caused variable inhibition, p-chloromercuri benzoate and n-ethylmaleimide resulted in noncompetitive inhibition.