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Purification of gamma-glutamyltransferase by phenyl boronate affinity chromatography. Studies on the acceptor specificity of transpeptidation by rat kidney gamma-glutamyltransferase.

gamma-Glutamyltransferase has been purified from rat kidney by a novel procedure using phenyl boronate affinity chromatography. The highly purified enzyme has been studied with respect to acceptor specificity for a number of amino acids, amino acid analogues, dipeptides and tripeptides. The acceptor activity is specific for L-amino acids. The amino acids and the majority of the essential amino acids are poor acceptors while the sulphur-containing amino acids are the best acceptors. The acceptor activity is modulated by the substitution of the amino acid side chain. Substitution of the side chain at the delta, gamma or beta positions results in a proportionally decreasing ability to act as acceptor. The carbonyl moiety of the gamma-carboxy group of the acceptor appears to be essential for acceptor activity, absence of an alpha-carboxy carbonyl group increases the Kappm of the acceptor approximately 100-fold.