L-PHENYLALANINE EFFECT ON RAT-BRAIN ACETYLCHOLINESTERASE AND NA-ATPASE(,K+)

The effect of different L-phenylalanine (Phe) concentrations (0.1-12.1 mM), on acetylcholinesterase (AChE) and Na+,K+-ATPase activities of b rain homogenate and pure enzymes, was investigated at 37 degrees C. AC HE and Na+,K+-ATPase activities were determined according to Ellman G. L., Courtney D., Andres V. and Featherstone R. M. (1961), Biochem. Ph armacol, 7, 88-95 and Bowler K. and Tirri R. (1974), J. Neurochem. 23, 611-613) respectively, after preincubation with Phe. ACHE activity in brain homogenate or in pure eel E.electricus enzyme showed a decrease , which reached up to 18% with concentrations of 0.9-12.1 mM. Brain ho mogenate Na+,K+-ATPase activity showed an increase 16-65% with 0.24-0. 9 min of Phe, while an activity increase of 60-65% appeared with 0.9-1 2.1 mM of Phe. Pure enzyme activity (from porcine cerebral cortex) was not affected by high Phe concentrations, while it was increased by lo w concentrations. The above results suggest: a) A direct effect of Phe on ACHE, b) A direct effect of low Phe concentrations and an indirect effect of high ones on Na+,K+-ATPase.