Release of 14C-tyrosine from tubulinyl-14C-tyrosine by brain extract. Separation of a carboxypeptidase from tubulin-tyrosine ligase

ARGARAÑA C.E.; BARRA H.S.,; CAPUTTO R.

SPRINGER

Año: 1978 vol. 19 p. 17 - 17

he carboxypeptidase previously described that releases tyrosine from tubulinyl-tyrosine was obtained from rat brain preparation free of tubulin-tyrosine ligase. The enzyme was purified 24-fold. Its activity was increased by 2 mM MgCl2 or 30 mM KCl. Mercaptoethanol (50 mM), colchicine (0.2 mM) and tyrosine (0.2 mM) showed practically no effect on the release of tyrosine whereas iodoacetate (2 mM), deoxycholate (0.5%), CuCl2 (0.1 mM), ZnCl2 (0.1 mM) and NaCl or KCl (240 mM) had a strong inhibitory effect. The optimal pH of this enzyme was 6.3-7. A preparation containing tubulin-tyrosine ligase free of carboxypeptidase was also obtained. This preparation catalyzed the release of tyrosine from tyrosinated tubulin in the presence of ADP, Mg2+, K+ and Pi and the incorporation of tyrosine into tubulin. For the releasing activity the optimal concentration of MgCl2 was 3--20 mM and of KCl was 10--30 mM. For ADP the maximal act;vity was at 0.3 mM or higher. An important difference between the a