K(+)-p-nitrophenylphosphatase activity in rat brain and liver.
K(+)-p-nitrophenylphosphatase (K(+)pNPPase) is the enzyme, which is considered to be involved in K(+)-dependent hydrolysis of the phosphoenzyme in the reaction cycle of Na(+), K(+)ATPase. The aim of our present study was to characterize some features of K(+)pNPPase in homogenates of the rat brain and liver. We determined p-nitrophenylphosphatase (pNPPase) activity in the presence of various ion combinations (Mg(2+)+ K(+), Mg(2+), K(+)). We found a higher total pNPPase activity in the brain (0.8+/-0.079 nkat/mg protein) than in the liver (0.08+/-0.01 nkat/mg protein). Contrary to the liver, the main part of the total brain activity was K(+)-dependent. The activity of K(+)pNPPase was significantly higher in cerebral cortex homogenates (0.86+/-0.073 nkat/mg protein) in comparison to those of the whole brain (0.57+/-0.075 nkat/mg protein). The specific K(+)pNPPase activity was two times higher in the isolated pellet fraction (0.911+/-0.07 nkat/mg protein), rich in synaptosomes, compared to the whole brain homogenate (0.57+/-0.075 nkat/mg protein). Our results demonstrate the high activity of K(+)pNPPase in the brain tissue and its distribution mainly into the pellet fraction, what might indicate a possible role of K(+)pNPPase in specific structures of the brain, e.g. in synaptosomes.
Ďurfinová
M
M
Department of Medical Chemistry, Comenius University, Faculty of Medicine, Bratislava, Slovak Republic. durfinova1@post.sk
Brechtlová
M
M
Líska
B
B
Barošková
Z
Z
D009597:4-Nitrophenylphosphatase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000201:enzymology
D009597:4-Nitrophenylphosphatase; D008274:Magnesium; D011188:Potassium; D002118:Calcium