Lysine and arginine represent a subset of basic amino acids with distinct catabolic pathways; lysine is predominantly ketogenic via saccharopine conversion, while arginine serves both glucogenic roles in the urea cycle and biosynthetic precursors for nitric oxide, creatine, polyamines (putrescine, spermidine), and proline. The metabolic fate of these residues defines their physiological functions, including collagen cross-linking via hydroxylysine, neurotransmission through endothelial-derived relaxing factor, immune defense mechanisms involving inducible nitric oxide synthase isoforms, and cellular proliferation regulated by polyamine synthesis rates. These pathways illustrate the integration of amino acid metabolism into energy homeostasis, structural integrity, signaling cascades, and host-pathogen interactions within biochemical systems.
Lysine and arginine represent a subset of basic amino acids with distinct catabolic pathways; lysine is predominantly ketogenic via saccharopine conversion, while arginine serves both glucogenic role…