KINETICS OF ALANINE REVERSAL ON THE INHIBITION OF NA-ATPASE ACTIVITY BY PHENYLALANINE AND PHENYLLACTATE IN THE SYNAPTIC PLASMA-MEMBRANE FROM THE CEREBRAL-CORTEX OF RATS(,K+)

Na+,K+-ATPase is involved in maintaining membrane potential and cellul ar integrity in the brain. It is inhibited in vitro by phenylalanine a nd its metabolites. This inhibition is reversed by alanine. We have in vestigated the kinetics of alanine reversal of the inhibitory action o f phenylalanine and phenyllactate on Na+,K+-ATPase. We found that alan ine had no effect on the enzyme activity and that it competes with phe nylalanine and the phenyllactate for the same site in the enzyme. We a lso assessed the interaction between phenylalanine and phenyllactate i n terms of their inhibitory action on Na+,K+-ATPase and found that bot h metabolites act at the same site of the enzyme. (C) 1998 Chapman & H all Ltd.