*4.2.4 Amino acid metabolism*

AAs have a significant impact on immune cell metabolism. They contribute to glycolysis by increasing translocation of GLUT1/GLUT4 (by leucine and isoleucine) to the cell surface and also by activating a glycolytic enzyme pyruvate kinase muscle enzyme 2, PKM2 (by serine). Glutaminolysis, i.e., conversion of glutamine into glutamate, is a basic and widespread metabolic process linking OXPHOS, redox regulation, and biosynthetic pathways (protein, nucleotides and branched chain FAs [44]. Glutamate, the first product of glutamine decomposition, can either aid in *de novo* synthesis of glutathione (GSH) to balance oxidative stress, or get converted into α-KG and enter the Kreb's cycle to generate ATP, mitochondrial ROS, and biosynthetic precursors. Hence, the varied end-products of glutamate, by generating counteracting metabolites, i.e., GSH and ROS, enable meticulous synchronization of metabolic flux. AA-derived metabolic products like α-KG and 2-HG assist in chromatin remodeling by affecting histone and DNA modifications [42].
