DESIGN OF SPECIES-SPECIFIC OR ISOZYME-SPECIFIC ENZYME-INHIBITORS .3. SPECIES AND ISOZYMIC DIFFERENCES BETWEEN MAMMALIAN AND BACTERIAL ADENYLATE KINASES IN SUBSTITUENT TOLERANCE IN AN ENZYME-SUBSTRATE COMPLEX

N6-and 8-substituted adenosine 5ʹ-triphosphate (ATP) derivatives have been synthesized and studied as potential species-or isozyme-selective inhibitors with Escherichia coli adenylate kinase (AK), the rat liver AK isozymes II and III, and the rat muscle AK isozyme. Substituent tolerance in the enzyme-ATP complexes was assessed from substrate properties, apparent enzyme-inhibitor dissociation constants (Ki; values; for inhibitions competitive with respect to ATP), and I50, values (for noncompetitive inhibitions). 8-SCH33-ATP and 8-S-n-C3H7ATP were not substrates of muscle AK and gave I50m = 6.0 and 6.2 mM, respectively; 8-SC2H5-ATP and 8-S-n-C3H7-ATP gave I50= 5.9 and 4.7 mM, respectively, with E. coli AK. In contrast, 8-SR-ATP (R = CH3,6H6, and n-C3H7) were substrates (Vmax= 5-16% that of ATP; Ku = 0.04-0.18 mM, ATP = 0.09 mM) and gave Ki= 0.05-0.36 mM with AK II and III. 8-SR-ATP [R = rc-C4H9, n-C5H11, CH2CH2OH, (CH2)3OH, and C6H6] gave K= 0.06-0.32 mM with AK II and III. N6-(CH2)5NHCOCH2I-ATP was a substrate of AK II and III (Vmax= 21 and 9%, respectively, that of ATP) but not of the muscle AK, and with E. coli AK it gave 7W = 4.75 mM. N6-(CH2)6NHCOCH3-ATP gave K, = 4.75 mM with AK III and 1%, = 12.9 mM with muscle AK. These results, and previous findings with thymidine kinase variants, demonstrate the ability of simple substrate substituents to influence binding or lack of binding to a substrate site in a markedly species-or isozyme-selective manner. © 1979, American Chemical Society. All rights reserved.