Synthesis and aminoacyl-tRNA synthetase inhibitory activity of prolyl adenylate analogs

Two nonhydrolyzable prolyl adenylate analogs, 5'-O-[N-(L-prolyl)-sulfamoyl]adenosine (L-PSA) and 5'-O-[N-(D-prolyl)-sulfamoyl] adenosine (D-PSA), were prepared in three steps from 2',3'-di-O-isopropylideneadenosine. Both of these compounds inhibited the in vitro activity of Escherichia coli and human prolyl-tRNA synthetase (ProRS). The human enzyme used in this study was derived from the carboxy-terminal domain of the multifunctional human EPRS gene. The K-i(ATP) values for L-PSA, determined using the ATP-PPi exchange assay, are very similar for both synthetases (approximate to 1-2 nM). The K-i(Pro) values, on the other hand, vary approximately seven-fold between the two synthetases (0.6 nM for human and 4.3 nM for E. coli). The K-i values measured for the D-PSA analog are much higher (51-470 nM) for all cases examined; however, the same species-specific differences are observed with respect to K-i(Pro). These results indicate possible structural differences in or near the active sites of the two enzymes that may be exploited in the future design of compounds that function as species-specific synthetase inhibitors in vivo. (C) 1996 Academic Press, Inc.