Abstract
Effects of heavy metals and alkaline earths on serum cholinesterase (pseudocholinesterase, pchE, EC 3. 1. 1.8) were studied. Eight metal ions (10-40 mM) of Ca++, Mg++, Ba++, Mn++, Co++, Cr+++, Cd++and Cu++ stimulated or inhibited the pchE activity. Changes in Ca++ and Mg++ around a physiological levels (2.0-5 mM) also influenced the pchE actvity. The influences (inhibition or stimulation) on the pchE activity by seven metal ions except of Cr+++ were relaxed by pooled human serum or serum protein such as albumin, α-globulin or γ-globulin. Ultrafiltration of the pchE solution which had been stimulated with Ca++ or Mg++ eliminated the metal ion and non-filtered pchE solution showed an original enzyme activity, suggesting a loose binding of metal ion with the pchE molecule and a reversible metal-induced influence. The present results suggest that changes in Ca++ or Mg++ level in the body fluid containing relatively poor proteins may influence the pchE activity in clinical examination.
