On the stability of isocitrate lyase from Pinus pinea.

Isocitrate lyase is a key catalyst of the glyoxylate cycle. A feature of the enzyme from higher plants is the high instability, that causes innumerable problems in working for characterization of the enzyme. The present communication demonstrates that the optimal conditions for the storage of isocitrate lyase from Pinus pinea are: the use of a low temperature (possibly below -20 degrees C), the realization of a high endogenous protein concentration of the enzyme preparations, or, above all when long storage conservation is necessary, the preservation of the enzyme in dried form (acetone precipitation), under vacuum at 4 degrees C. The data reported in this paper seem to exclude, in the above studied conditions, a role for serine proteases in the destabilization of the enzyme. The thiol compounds are not determinant and no effect is obtained by adding exogenous proteins (serum albumin, beta-fructosidase).