Inhibitory effects of beta-hydroxyethyl 2,4-dinitrophenyl disulphide on rat brain cholinesterase activity.

: Hydrolysis of 1-6 mM AChJ by rat brain homogenates in TRIS-HCl buffer, pH 7-8, supplemented with NaCl and MgCl2, was found to be suppressed by a half by pretreatment with 0-3 mM beta-hydroxyethyl 2,4-dinitrophenyl disulphide (HEDD), a reagent for SH groups. This effect has been shown to be due to partial inhibition of a Phg-sensitive esterase which has been characterized as AChE on the ground of experiments with MeCh and BuCh. Similar inhibition of AChJ hydrolysis was also noted on pretreatment of brain homogenates with 0-05 M N-ethylmaleinimide (NEM). The inhibition degree has turned out to depend upon either AChJ concentration (0-1--4-8 mM) and duration of contact of the tissue with HEDD before addition of the substrate. The AChE activity revealed in 0-2 mM AChJ was found to be particularly sensitive to HEDD. Sensitivity of rat brain AChE to either HEDD and NEM may indicate for occurring of SH in some one its isozyme. No less, other mechanisms of the inhibition, particularly possibility of interaction of HEDD with a disulphide group must be also considered.