Kent Axelsson

An essential role of cytosolic thioltransferase in protection of pyruvate kinase from rabbit liver against oxidative inactivation

Pyruvate kinase from rabbit liver is inactivated spontaneously in the presence of air. Glutathione in physiological concentrations gives partial protection against inactivation. Full protection is obtained with glutathione and purified cytosolic thioltransferase supplemented with a glutathione‐regenerating system. It is suggested that thioltransferase plus glutathione serve a general function in protecting protein thiol groups against oxidation.

Synthesis of a mixed disulfide of egg white lysozyme and glutathione - a model substrate for enzymatic reduction of protein mixed disulfides

A considerable proportion of the endogenous GSH has been demonstrated to be bound as mixed disulfides to proteins in cells [l-4] . The functional importance of such mixed disulfides is so far not well established, but one function which can be proposed is the modulation of the biological activity of specific proteins. Another possibility is that protein mixed disulfides can serve as a reservoir of GSH, which can regulate the concentration of mobile GSH. Such a system involving free and protein-bound GSH has the capacity to act as a redox buffer. However, the study of the biological function of protein mixed disultides has been limited by the lack of suitable experimental systems. Current research in our laboratory aims at the elucidation of the biochemical reactions which effect the release of GSH from protein mixed disulfides. The present paper describes the synthesis of a mixed disulfide of lysozyme and GSH, which is suitable as a model compound in such studies, and recent work [5] describes how this compound can be reduced by an enzyme present in rat liver cytosol.