Inactivation of yeast ornithine decarboxylase by polyamines in vivo does not result from the incorporation of polyamines into enzyme protein

Abstract

We have previously reported that addition of spermidine and spermine to a culture of Saccharomyces cerevisiae results in loss of ornithine decarboxylase activity even though there is no loss of enzyme protein. These findings indicate that the loss of activity is due to a post-translational modification of the enzyme. Since transglutaminase has been shown to catalyze the incorporation of putrescine into ornithine decarboxylase in vitro with resultant loss of enzymatic activity [[17.] Biochem. Biophys. Res. Commun. 99, 1167-1172], we decided to see if the inactivation we observed in vivo was caused by such incorporation. We found that this is not the case; i.e., after growth of yeast with added amines, the inactivated ornithine decarboxylase contains no covalently-bound spermidine or spermine. Thus, we conclude that transamidation by transglutaminase does not play a role in vivo in the polyamine-mediated post-translational modification of yeast ornithine decarboxylase.