SIR2: The Biochemical Mechanism of NAD+-Dependent Protein Deacetylation and ADP-Ribosyl Enzyme Intermediates

Abstract

The Sir2 family of enzymes is a recently described class of NAD(+)-dependent protein deacetylases that use NAD+ as a reactant to deacetylate acetyllysine residues of protein substrates to form the aminolysine sidechain and a novel product 2'-O-acetyl-ADP-ribose. The founding member of the Sir2 proteins, the yeast Sir2p, has been identified as a key member of SIR complexes responsible for the long-term silencing of genes in the yeast Saccharomyces cerevisiae. Increase of Sir2 activity by caloric restriction or osmotic stress increases genome stability and lifespan in this organism. The Sir2 reaction mechanism couples ADP-ribosyltransfer and hydrolysis reactions via the formation of a stabilized ADPR-peptidyl intermediate. Principles of the chemistry of stabilized ADPR intermediates are examined for Sir2 and the mechanistically related ADP-ribosylcyclase CD38. An examination of the crystal structures of Sir2 family members is presented with a view to the chemical requirements of the Sir2 reaction. The present review describes the current knowledge of the Sir2 reaction, the reaction mechanism and the regulation of Sir2.

SIRT1 Deacetylation and Repression of p300 Involves Lysine Residues 1020/1024 within the Cell Cycle Regulatory Domain 1

“…1C). Nicotinamide, an inhibitor of the NAD-dependent deacetylase activity of SIRT1 (27)(28)(29)(30)(31)(32), abrogated SIRT1 repression of Gal4-p300 transactivation at a dosage of 5 mM but had no effect on Gal4-p300 activity in the presence of the empty vector or the inactive SIRT1(H363Y) mutant (Fig. 1C).…”

“…The HDACs in class I and class II are characterized by their sensitivity to the inhibitor trichostatin A (TSA). In contrast, the HDAC activity of the class III sirtuins is not inhibited by TSA, but is NAD-dependent and inhibited by nicotinamide (27)(28)(29)(30)(31)(32).…”

“…SIRT1, the closest mammalian ortholog of the yeast SIR2 gene, functions as an NAD-dependent deacetylase of a number of nonhistone substrates including p53 (37)(38)(39). The enzymatic activity of SIR2 is regulated by the availability of the oxidized form of NAD ϩ allowing SIR2 to function in part as a redox or metabolic sensor (30). SIRT1 represses p53-mediated transcription and deacetylates the p53 protein at lysine 382, impairing its ability to activate the apoptotic program (37)(38)(39).…”

SIRT1, an Antiinflammatory and Antiaging Protein, Is Decreased in Lungs of Patients with Chronic Obstructive Pulmonary Disease

“…Recently, it has been shown that SIRT1 plays an important role in a wide variety of processes, including stress resistance, metabolism, apoptosis, senescence, differentiation, and aging (9). SIRT1 negatively regulates transcription factors, such as nuclear factor (NF)-kB, in the nucleus by the deacetylation of modified lysine residues on histones, transcription factors, and other nonhistone proteins (16)(17)(18). Recently, it has been shown that SIRT1 regulates NF-kB-dependent transcription and cell survival in response to tumor necrosis factor (TNF)-a (19).…”

Flexizymes-facilitated Genetic Code Reprogramming Leading to the Discovery of Drug-like Peptides

“…This reaction gives the corresponding deacetylated peptide/protein and 2¤-Oacetyl-ADP-ribose (Figure 8a). 70,71 Based on this mechanism, a peptide inhibitor of SIRT2 was designed based on a substrate peptide in which the ε-N-acetyl group of the K Ac residue was replaced with an ε-N-trifluoroactyl group (K Tfa ). This replacement of K Ac with K Tfa reduced the rate of formation of the reaction intermediate by nearly six orders of magnitude.…”