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Adenosine 5'-triphosphate (ATP) derivatives bearing iodoacetylamino-n-alkyl substituents [(CH2)nNHCOCH2I] on N6 were synthesized as potential ATP-site-directed irreversible inhibitors of adenylate kinases from rabbit, pig, and carp muscle. When n was 5 no enzyme was progressively inhibited (inactivated) by 1 mM inhibitor under the test conditions (6 h at 0 degrees); when n was 6 the rabbit enzyme was 76% inactivated by 0.79 mM inhibitor whereas the pig and carp enzymes were unaffected by 2.76 mM inhibitor; when n was 7, 1 mM inhibitor inactivated 14% of the rabbit enzyme and did not inactivate the pig and carp enzymes; when n was 8, all enzymes were inactivated 11-15% by 1 mM inhibitor. No inactivation occurred when the iodine of the hexamethylene analogue was replaced by hydrogen. The selective effect occured also in mixtures of the rabbit and pig enzymes and evidence could not be found that the hexamethylene analogue was activated by the rabbit enzyme or deactivated by the pig and carp preparations. The species-specific inactivation in concluded from various lines of evidence to be ATP-site-directed and is attributed to alkylation of an amino acid residue of the rabbit enzyme which in the pig and carp enzymes is absent, inaccessible, or less reactive. These and previous studies with several other enzymes provide evidence that substrate-site-directed agents capable of bonding covalently to an amino acid residue outside the substrate site can be designed to exert species-specific or tissue-specific irreversible inhibition of target enzymes.

. Can. J. Chem. 55,4257 (1977). Several polypeptides have been synthesized which contain the alternating sequence lysyl-X, where X = gly, L-ala, D-ala, L-val, L-leu, and L-phe. The polypeptides have been characterized by gel filtration (molecular weight) and by circular dichroism spectroscopy (secondary structure).LEWIS A. SLOTIN, DENIS R. LAUREN et Ross E. WILLIAMS. Can. J. Chem. 55,4257 (1977). Nous avons synthktise plusieurs polypeptides qui contiennent la sequence alternke lysyl-X, ou X = gly, L-ala, D-ala, L-val, L-leu et L-phe. Les polypeptides ont ktk caractkrises par des filtrations sur gel (poids molkculaire) et par des spectres du dichroisme circulaire (structure secondaire).

N6-O- and p-fluorobenzoyladenosine 5'-triphosphates (IIIc and IIc, respectively) have been synthesized as potential adenosine 5'-triphosphate (ATP) site-directed reagents for enzymes. IIc and IIIc were substrates of yeast hexokinase; neither they nor the corresponding ADP derivatives inactivated yeast hexokinase or rabbit pyruvate kinase. IIc rapidly inactivated rabbit and carp muscle adenylate kinases; the effect is probably ATP site directed because N6-benzoyl-ATP did not inactivate and was a substrate (Vmax = 28 and 10%, respectively, that of ATP), and because of ATP retarded the inactivation. The inactivations followed pseudo-firsr-order kinetics; in the presence of 2.64 mM ATP at 0 degrees the half-life of the rabbit kinase was 210 min with 50 muM IIc and the half-life of the carp kinase was 130 min with 100 muM IIc. Adenylate kinase of pig muscle was inactivated by IIc in a manner similar to the rabbit and carp enzymes except that the rate of inactivation exhibited an inflexion. IIIc inactivated rabbit, pig, and carp adenylate kinases by pseudo-first-order kinetics; the rate constants for inactivation at 0 degrees were 9.1 X 10(-3), 1.3 X 10(-3), and 1.9 X 10(-3) min-1 and the apparent dissociation constants (K) of the IIIc-enzyme complexes were 710, 970, and 720 muM, respectively. From the substrate properties of IIIc alone and in admixture with ATP its dissociation constants (Ki) from the ATP sites of the enzymes were found to be 500, 700, and 845 muM, respectively. The similarity between the K and Ki values, together with marked retardation of the inactivations by ATP, indicates that IIIc is an ATP-site-directed reagent for the three adenylate kinases.