AMINO ACIDS AS METABOLIC REGULATORS
In this analytical review the regulation and synchronization principles of metabolic processes in mammalian cells were studied. It was used a model of cell metabolism as a two-componential system, which includes a controlling signaling system (that regulates the main enzymatic systems), and an executive metabolic system (that directly performs biosynthesis). This consideration allowed us to distinguish two transitional metabolic states (transition from catabolism to anabolism and vice versa), in which the main changes in the signaling system occur. The signaling system of natural amino acids (AAs) was selected for review as the most convenient fragment of the cell metabolism, since AAs are involved in both signaling and executive metabolic subsystems. A graphical method for representation of signaling events was developed in the work. It made possible to demonstrate the processes sequence occurring in both metabolic subsystems during the passage of a complete metabolic cycle by a non-dividing cell. An important feature of the AA signaling system was revealed: their signal properties are determined not only by molecular structure, but also by their location in the cell. Four main signaling groups of AAs were determined: localized in lysosomes, mitochondria, cytosol, and extracellular space near the plasma membrane. These AA groups are similar in composition, but have different receptors. The scheme of metabolism regulation by AAs was constructed in this work and can serve as basis for the development of a more complete spatio-temporal scheme of metabolic regulation, which includes a wide variety of other intracellular signaling cascades.