| SIRT4 resides within the sirtuin family of NAD+-dependent enzymes, primarily localizing to mitochondria where it exerts regulatory control over metabolic processes distinct from classical deacetylase functions. SIRT4 adopts a conserved catalytic core that accommodates diverse substrates through flexible active site geometry, enabling deacylation, ADP-ribosylation, and lipoamidase activities alongside selective deacetylation. Enzymatic action targets malonyl CoA decarboxylase through deacetylation at specific lysine residues, thereby inhibiting its conversion of malonyl CoA to acetyl CoA and sustaining malonyl CoA pools that allosterically suppress carnitine palmitoyltransferase-1 to curtail fatty acid oxidation while favoring lipogenesis under nutrient-replete states. SIRT4 further modifies glutamine dehydrogenase via ADP-ribosylation, constraining glutaminolysis and TCA cycle anaplerosis to preserve mitochondrial redox balance and limit proliferation signals in response to genotoxic stress. Interaction with the pyruvate dehydrogenase complex occurs through delipoamidation of the E2 subunit dihydrolipoyllysine acetyltransferase, disrupting PDH flux and redirecting carbon toward oxidative phosphorylation or antioxidant defenses during energy crises. SIRT4 coordinates lipid homeostasis in skeletal muscle and adipose tissue by repressing catabolic shifts, while in tumor cells, it couples DNA damage sensing to metabolic arrest via glutamine restriction, activating AMPK-p53 phosphorylation cascades that induce autophagy and suppress Warburg reprogramming. Reduced SIRT4 activity accompanies accelerated tumorigenesis across pancreatic, prostate, and colorectal cancers, where unchecked MCD activation and glutamine flux fuel biomass accumulation and metastatic dissemination. |
Lane 1: Neuro-2a, Lane 2: C2C12, Lane 3: RAW264.7, Lane 4: NIH/3T3
