The effect of thiol and other group-specific reagents on erythrocyte and plasma cholinesterases

Abstract

Although the cholinesterases of human blood were moderately sensitive to arsenite and iodine, and were usually inhibited by other heavy metal reagents in sufficiently high concn., they differed from typical -SH enzymes in being either much less sensitive or quite insensitive to most -SH reagents tried. Further, arsenite inhibition was reduced by pH, not increased as would be expected if a thio-arsenite link had been formed. It is concluded that these cholinesterases are in all probability not -SH enzymes and that there is also no evidence for the participation of metal ions, carbonyl groups or carboxylate groups in the active center.