Helia O

Inter-tissue and inter-species comparison of butyrylcholinesterases

Butyrylcholinesterase (BuChE) occurs in a multiple molecular forms whose catalytic activity depends on tissue distribution and species. The hypothesis led us to the study of BuChE catalytic properties focused on the inter-tissue and inter-species level with benzoylcholine and N-alkyl derivates of benzoylcholine (BCHn) as substrates. These compounds are soft disinfectants easily biodegradable to biologically inactive hydrolytic products, substituted choline and benzoic acid. Different sources of BuChE were used: rabbit and rat liver microsomal fraction (membrane-anchored enzyme) and serum (soluble form). Hydrolytic activity of both these BuChE forms was compared to rat recombinant BuChE (rBuChE). Hydrolytic product (benzoic acid) formation was recorded as function of time, and hydrolytic rate was determined. Tissue distribution of BuChE plays an important role in hydrolysis of BCHn. High BuChE activity was observed in a serum of both studied species rat and rabbit and was significantly dependent on a structure of substrates. Activity of soluble serum forms was the same as that for the rBuChE. Significant change of BuChE activity was recorded on the inter-species level in the microsomal fractions. It is because the rabbit microsomal BuChE activity had absolutely different course for all substrates as compared to rat microsomes. Inhibitory studies of BCHn enzymatic hydrolysis of all BuChE forms were performed to determine the level of BuChE participation in BCHn hydrolysis. It can be concluded that short-chain BCHn substrates are exclusively hydrolyzed by BuChE from all studied sources except for the rabbit liver microsomal fraction. Rabbit seems to have different enzymes involved in the hydrolysis of all studied BCHn compounds.

THe effect of γ,γ-BIS-4-ethylphenyl-α, β-dibromoisocrotonic acid on ehrlich ascites carcinoma and yeast cells

Abstract In Ehrlich ascites carcinoma (EAC) cells γ,γ-bis-4-ethylphenyl-α,β-dibromoisocrotonic acid (EPBC) inhibits after short exposure the incorporation of [14C]valine. [14C]adenine and [14C]thymicline, the rate of inhibition being directly related to the concentration of the inhibitor. This inhibition occurs even at concentrations of EPBC which stimulate the endogeneous respiration of the cells as well as the consumption of glucose and the formation of lactate. Higher concentrations fully depress the endogeneous respiration and glycolysis and cause loss of transplantability of EAC cells. The attack on glycolysis is multitarget in character. The activities of several enzymes dependent on free sulfhydryl groups, especially glyceraldehyde-3-phosphate dehydrogenase, glucosc-6-phosphatc dehydrogenase and phosphofructokinase, are inhibited by EPBC. The changes in the total sulfhydryl group content and other findings suggest the existence of direct chemical reaction of EPBC with thiol groups. The same mechanism may explain also the effect of EPBC on glycolysis in yeast cells.