Phylogenetic tree of the silent information regulator 2 (Sir2) like protein family. The evolutionary tree of cow (co), pig (pi), dog (do), cat (ca), human (hu), mouse (mo), chicken (ch), zebrafish (ze), and Saccharomyces cerevisiae (s.c) sequences for sirtuin (SIRT)1, SIRT3, and Sir2 was made with the unweighted pair group method with arithmetic mean method using GENETYX-win Ver.9.1.0 (GENETYX Corp). The data base accession nos. for each amino acid sequence used in this analysis are described in Figure 1. The bars and values of 0.1 in the figure represent evolutionary distances.