POLYAMINE BIOSYNTHESIS AND FUNCTION

多胺，腐胺，亚精胺，还有

The polyamines, putrescine, spermidine, and spermine, are major polybasic compounds in all living cells. These amines have been shown to be important for many systems related to growth and differentiation. We have been interested in how these polyamines are synthesized, how their biosynthesis and degradation are regulated, their physiologic functions, and how they act in vivo. For this purpose we have constructed null mutants in each of the biosynthetic steps in both Escherichia coli and in Saccharomyces cerevisiae.. Our present studies are directed at extending our studies on the biochemistry, regulation and genetics of these amines and of the biosynthetic enzymes in S. cerevisiae. During the current year we have been particularly interested in studying the regulation of the enzyme ornithine decarboxylase which is a key enzyme in the formation of the polyamines, and is of special interest in studies on the physiological function of the polyamines. The ornithine decarboxylase levels are repressed by the addition of spermidine to the medium, and we have found that, contrary to previous reports in the literature, an important part of this regulation involves the induction of a proteolytic activity. Interestingly this induction does not occur if protein synthesis is inhibited, indicating the involvement of a new, and, as yet unidentified, protein. Other studies have involved: (1) the effect of polyamine deficiency on the ribosomal pattern as part of our ongoing studies on the role of the polyamines in protein biosynthesis, and (2) in collaboration with Arthur Kornberg a quantitative comparison of polyamine levels and polyphosphate levels in E. coli and S. cerevisiae, using our polyamine-requiring mutants and Kornberg's mutants in the polyphosphate pathways in yeast.