Carbon and nitrogen metabolism and reversible protein phosphorylation

Publisher Summary This chapter focuses on the regulation of activity of several enzymes involved in carbon- and nitrogen-metabolisms that are phosphorylated by either calmodulin-like domain protein kinases (CDPKs) or sucrose nonfermenting-1 (SNF1)-related protein. Coordination between carbohydrate metabolism and nitrogen assimilation is essential to avoid direct competition, and it potentially involves control at several levels including gene expression, membrane transport, and enzyme activity. One important mechanism that may impact all three levels is reversible protein phosphorylation. Recent studies have also identified several other enzymes, including trehalose-6-phosphate synthase and glutamine synthetases, as phosphoproteins because they interact with 14-3-3 proteins in a phosphorylation-dependent manner. Several transport activities that may impact metabolism either directly or indirectly may also be controlled by phosphorylation. Of particular importance is the possible regulation by phosphorylation of ion and solute transport, for example, the plasma membrane H + -adenosine triphosphate (ATP)ase, plasma membrane K + channel, and the sucrose transporter.