Differential acetylcholinesterase activity in rat cerebrum, cerebellum and hypothalamus.

Acetylcholinesterase (AChE) has been purified from three different regions of rat brain using Sephadex G 200 column. SDS PAGE (6%) showed single band for the purified AChE fractions. Purified and lyophilized AChE from different (NH4)2SO4 precipitated fractions of three brain parts were utilized for in vitro enzyme kinetics using Dimethoate (Dmt) as inhibitor. K(m) values for cerebellum and hypothalamus were almost similar whereas cerebrum showed a different K(m) value compared to other two regions. With the drug Rivastigmine it was found that % G1 and G4 forms of AChE in three different parts of brain are different.

Phosphorylation of casein, fibrinogen and calmodulin by a glycoprotein protein kinase from monkey cerebellum: a casein kinase II-like enzyme.

A glycoprotein protein kinase was isolated from monkey cerebellum by polylysine-Sepharose chromatography and affinity chromatography on Sepharose 4B coupled to the lectin, Concanavalin A. The protein kinase phosphorylated casein on serine and threonine residues and was stimulated by polylysine, polyarginine, spermine, histone, protamine and sphingosine, but was inhibited by heparin, poly (Glu, Ala, Tyr) and poly (Glu, Tyr). These characteristics were typical of casein kinase II. The protein kinase also phosphorylated fibrinogen and calmodulin and exhibited similar characteristics of stimulation by polylysine or polyarginine. The phosphorylation of fibrinogen (a glycoprotein), but not casein or calmodulin (non-glycoproteins), was significantly inhibited by Concanavalin A. Unlike casein kinase II, the enzyme did not undergo autophosphorylation. The collective results suggested that the enzyme from monkey cerebellum was a casein kinase II-like protein kinase and that phosphorylation of a glycoprotein substrate (fibrinogen) by the kinase could be influenced by a carbohydrate binding lectin.

Effect of soman administration on beta-esterases in blood, liver microsomes and brain regions of rats.

Activities of enzymes cholinesterase (ChE) and carboxylesterase (CaE) were assayed in serum, liver microsomes and three regions of brain, viz; cerebrum, cerebellum and brain stem (with mid brain) in male albino rats at 0.5 and 2 h periods after administration of 1/2 LD 50 dose of soman (0.22 mg/kg) intraperitoneally in olive oil as vehicle. At 0.5 h, in serum, ChE activity declined to 33% of its initial level whereas CaE activity was almost completely inhibited. However, in the liver microsomes at this period, ChE activity was greatly inhibited (18% of initial level) whereas CaE activity was nearly unaffected. At 2 h period, both the enzymes in the serum were almost completely inhibited. In the brain regions (excepting in cerebellum), both the enzymes were nearly similarly inhibited (by 55% to 65% of the initial level) at both the periods. The time related differential response of these two beta-esterases in acute soman intoxication probably occurred in the peripheral tissues like blood and liver but not in the CNS.

Atividade acetilcolemesterásica em encéfalos humanos / Acetylcholinesterase activity in human brain

Estudou-se a atividade acetilcolinesterásica (AChE 3.1.1.7) em várias áreas do encéfalo humano adulto nas fraçöes S1 (enzima solúvel) e S2 (enzima solubilizada). As concentraçöes enzimáticas mais elevadas foram detectadas no neostriado (9,2 micron moles ATC/mg proteina/h). Atividades enzimáticas menores foram obtidas no paleocerebelo, neocerebelo e paleo-estriado (3,3; 3,8 e 3,6 micron moles ATC/mg proteina/h), seguidos pelo arquicerebelo e neocórtex sensitivo (1,3 e 1,6 micron moles ATC mg proteina/h). Por outro lado, as menores concentraçöes enzimáticas foram observadas a nível de neocórtex motor, paleocórtex e arquicórtex que apresentaram uma atividade de 0,5; 0,5 e 0,9 micron moles ATC/mg proteina/h). Os valores de Km aparente foram de 1,4 x 10**-4M e 2 x 10**-4M para as fraçöes S1 e S2 respectivamente, obtidos de neoestriado. O cromatograma da fraçäo S1, submetida à filtraçäo, em Sepharose 6B mostrou 3 picos com atividade AChE sugerindo a presença de 3 espécies moleculares com pesos em torno de 417.000, 112.000 e 40.000 daltons