Esterase-like Activity of Human Serum Albumin. IV. Reactions with Substituted Aspirins and 5-Nitrosalicyl Esters

概要

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To elucidate the reactivity of the lysine-199 residue of human serum albumin (HSA) with ester-type drugs and to characterize the region near the lysine, the reactions of substituted aspirins and 5-nitrosalicyl esters with HSA were investigated kinetically at 25℃. The Michaelis constant (K_s in M) and the catalytic rate constant (k_2 in s^<-1>) were determined, and the relationship between these constants and the structure of the substrates was explored. For the reactions with substituted aspirins at pH 9.9,the logarithm of k_2 is correlated with the pK_a value of the hydroxyl group in the parent salicylic acid. The regression line is as follows : log k_2=-0.843pK_a+6.75 (r=-0.988). The K_s value is influenced by the number of substituents on the phenyl ring rather than the nature of the substituents. For the reactions with 5-nitrosalicyl esters at pH 7.4 the k_2/K_s values were correlated with Hansch's hydrophobic substituent constant π and Taft's steric constant E_s as follows : log (k_2/K_s)=0.423π+0.386E_s+1.35 (r=0.908).
社団法人日本薬学会の論文
1984-09-25