INTEGRATION OF METABOLISM IN NONPHOTOSYNTHETIC PLASTIDS OF HIGHER-PLANTS

Non-photosynthetic plastids are important subcellular sites for the as similation of inorganic nitrogen and the biosynthesis of amino acids, starch and fatty acids. Unlike chloroplasts, all the metabolites for t hese processes have to be imported from the cytoplasm either directly or indirectly. Many of the intermediates for biosynthesis are generate d by glycolysis and the oxidative pentose phosphate pathway within the se organelles. In this paper we summarize what is Known about the regu lation of oxidative oxidative and biosynthetic pathways within such pl astids. Emphasis is placed (I) on metabolite transport; (2) on competi tion for ATP and reductant; and (3) on competition for hexose phosphat e between biosynthetic and oxidative pathways.