Esterase-like activity of human serum albumin II: reaction with N-trans-cinnamoylimidazoles.
To elucidate the details of the esterase activity of human serum albumin, the reaction of N-trans-cinnamoylimidazoles with albumin was investigated kinetically at various pHs at 25 degrees. The reaction consisted of the acylation of albumin (probably the tyrosine-411 residue) by the substrate and the deacylation of cinnamoyl-albumin. The acylation was approximately 10--100-fold faster than the spontaneous hydrolysis of the substrate over the pH range examined. The pH profile for the deacylation rate constant indicated the participation of a group having a pKa of approximately 9.4. The deacylation was subjected to the effect of deuterium oxide. The electron-withdrawing substituent facilitated the deacylation; the Hammett rho value was 1.63. These results suggest that the deacylation proceeded via general base catalysis by this group.
D000215:Acylation; D004950:Esterases; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles; D007700:Kinetics; D012709:Serum Albumin
D007093:Imidazoles; D012709:Serum Albumin; C037552:cinnamoylimidazole; D004950:Esterases