NAD-dependent lysine demalonylase, desuccinylase and deglutarylase that specifically removes malonyl, succinyl and glutaryl groups on target proteins (PubMed:23806337, PubMed:21908771, PubMed:22076378, PubMed:24315375, PubMed:24703693). Activates CPS1 and contributes to the regulation of blood ammonia levels during prolonged fasting: acts by mediating desuccinylation and deglutarylation of CPS1, thereby increasing CPS1 activity in response to elevated NAD levels during fasting (PubMed:19410549, PubMed:24703693). Activates SOD1 by mediating its desuccinylation, leading to reduced reactive oxygen species (By similarity). Activates SHMT2 by mediating its desuccinylation (By similarity). Modulates ketogenesis through the desuccinylation and activation of HMGCS2 (PubMed:24315375). Has weak NAD-dependent protein deacetylase activity; however this activity may not be physiologically relevant in vivo. Can deacetylate cytochrome c (CYCS) and a number of other proteins in vitro such as Uox (PubMed:23085393). H2O + N(6)-malonyl-L-lysyl-[protein] + NAD(+) = 2''-O-malonyl-ADP-D-ribose + L-lysyl-[protein] + nicotinamide H2O + N(6)-succinyl-L-lysyl-[protein] + NAD(+) = 2''-O-succinyl-ADP-D-ribose + L-lysyl-[protein] + nicotinamide H2O + N(6)-glutaryl-L-lysyl-[protein] + NAD(+) = 2''-O-glutaryl-ADP-D-ribose + L-lysyl-[protein] + nicotinamide Binds 1 zinc ion per subunit. Monomer. Homodimer (By similarity). Interacts with CPS1 (PubMed:19410549). Interacts with PCCA (PubMed:23438705). Mainly mitochondrial. Also present extramitochondrially, with a fraction present in the cytosol and very small amounts also detected in the nucleus. Detected in brain, liver, heart, kidney, lung, thymus, spleen, skeletal muscle, intestine, pancreas and testis (at protein level). In contrast to class I sirtuins, class III sirtuins have only weak deacetylase activity. Difference in substrate specificity is probably due to a larger hydrophobic pocket with 2 residues (Tyr-102 and Arg-105) that bind to malonylated and succinylated substrates and define the specificity. Mice are born at an abnormal Mendelian ratio with the number of live-born pups reduced by 40% (PubMed:24076663). Surviving mice display a global protein hypersuccinylation and hyperglutarylation in both liver and skeletal muscle, while global lysine acetylation is not significantly impacted (PubMed:22076378, PubMed:24315375, PubMed:23806337, PubMed:24703693). Mice display elevated levels of blood ammonia during fasting, but otherwise are metabolically similar to wild-type (PubMed:24076663). No overt phenotype observed in mice on chow or high fat diet, suggesting that Sirt5 may be dispensable for basal homeostasis under these conditions (PubMed:24076663). After 48 hours of fasting, the absence of Cps1 activation leads to elevated blood ammonia levels, possibly due to the presence of succinylation at 'Lys-1291' in Cps1 (PubMed:22076378). Animals show a decrease of fatty acid oxidation and increase of acylcarnitines accumulation (PubMed:24315375). Belongs to the sirtuin family. Class III subfamily. The ability to deacetylate Uox in vivo is unclear. The anti-acetylated lysine antibody used in the assay is not fully specific and cross-reacts with some acylated lysines. It is therefore possible that it also recognizes N6-malonyllysine and N6-succinyllysine residues (PubMed:23085393).