A Structurally\nDiverse Compound Screening Library\nto Identify Substrates for Diamine, Polyamine, and Related Acetyltransferases

Spermidine/spermine <i>N-</i>acetyltransferases\n(SSATs)\nand other types of polyamine acetyltransferases (PAATs) acetylate\ndiamines and/or polyamines. These enzymes are evolutionarily related\nand belong to the Gcn5-related <i>N-</i>acetyltransferase\n(GNAT) superfamily, yet we lack a fundamental understanding of their\nsubstrate specificity and/or promiscuity toward different compounds.\nMany of these enzymes are known or are predicted to acetylate polyamines,\nbut in the cell there are other types of compounds that contain moieties\nderived from polyamines that may be the native substrates for these\nenzymes. To learn more about the identity of substrates that are acetylated,\nwe selected and screened 17 different GNAT enzymes for activity toward\na set of structurally diverse compounds that contained different types\nof amine moieties (<i>e.g.</i>, aminopropyl, aminobutyl, <i>etc.</i>). These compounds included diamines, triamines, and\npolyamines containing primary amino groups, and they had structural\ndiversity with variation of the chain length and presence or absence\nof internal amino groups and other functional groups. We found 12\nof the 17 enzymes acetylated at least one of the compounds. Some enzymes\nwere selective toward acetylating only one compound while others exhibited\nsubstrate promiscuity toward numerous compounds. Our experimental\nresults ultimately allowed us to pinpoint specific substrates that\ncould be further investigated to more fully understand substrate specificity\nversus promiscuity of GNAT enzymes and the role of acetylated small\nmolecules in cells.