Polyamines play an essential role in cell growth and differentiation, and their biosynthesis pathway may be an important target for design of chemotherapeutic agents. Ornithine decarboxylase (ODC) is the first and rate-limiting enzyme in polyamine biosynthesis. ODC is a highly regulated enzyme with contro] points at the level of transcription, translation and protein degradation. Indeed, ectopic expression of ODC conferred a transformed phenotype to mouse fibroblast. These results suggest that modulation of ODC activity is important for growth regulation. Recently a consensus sequence, (AIV)TLXT(T/S), has been identified which is present in all mammalian L-amino acid decarboxylases that are regulated by polyamines, has been detected. The objective of the proposed project is to characterize the role of this sequence in the regulation of ODC expression and activity. Transfection of cells with different ODC construct carrying specific mutations of this sequence will be use. The results of these studies will be extended to other selected L-amino acid decarboxylases.