Lorenzo A. Pinna

PHOSPHORYLATION BY CASEIN KINASE-2 AND REVERSIBLE ALTERATION OF THIOL GROUPS: MECHANISMS OF CONTROL OF ORNITHINE DECARBOXYLASE?

The regulation of ornithine decarboxylase (ODC) in mammalian cells appears to be complex and not completely clarified.1, 2 This enzyme is characterized by a very short half-life, but the mechanism of ODC degradation is as yet unknown3. Because of the rapid turnover, changes in the rate of synthesis are promptly expressed as fluctuations of ODC activity1, 4. However, a post-translational control of ODC has been proposed by several Authors1, and include interaction with a specific inhibitor, antizyme5, and interconversion between distinct charged species6. These mechanisms could account for the occurence of inactive ODC forms or play a function in the process of ODC decay, although their precise role remains to be defined. The present paper focuses on two additional covalent modifications of ODC molecule, which could cooperate at the control of ODC activity and decay: the reversible oxidation of sulphydrylic groups and the phosphorylation by a particular class of protein kinases, called casein kinase-2 (CK-2).