Fig. 1

NAD(H) and NADP(H) play a vital role in cellular metabolism. NAD(P)(H) are key coenzymes for cellular metabolism. Cytosolic NADH is produced during glycolysis, which is either consumed during conversion of pyruvate into lactate or transported into mitochondria by reducing equivalent shuttle pathways. Mitochondrial NADH is generated by oxidation of pyruvate and fatty acids and in the tricarboxylic acid cycle (TCA), and it is oxidized back into NAD⁺ by the electron transfer chain (ETC). Glycolysis and mitochondrial respiration supply energy production. NADPH is mainly produced by the pentose phosphate pathway and other metabolic enzymes whose isoforms exist in both the cytosol and mitochondria, and it is consumed for the synthesis of biomass and antioxidant defense responses. The NAD(H) and NADP(H) pools connect through NAD⁺ kinase (NADK) and nicotinamide nucleotide transhydrogenase (NNT). Abbreviations: glucose-6-P, glucose-6-phosphate; G-3-P, glyceraldehyde-3-phosphate; PEP, phosphoenolpyruvate; ribose-5-P, ribose 5-phosphate