ATP and ADP hydrolysis in brain membranes of zebrafish (Danio rerio).
Nucleotides, e.g. ATP and ADP, are important signaling molecules, which elicit several biological responses. The degradation of nucleotides is catalyzed by a family of enzymes called NTPDases (nucleoside triphosphate diphosphohydrolases). The present study reports the enzymatic properties of a NTPDase (CD39, apyrase, ATP diphosphohydrolase) in brain membranes of zebrafish (Danio rerio). This enzyme was cation-dependent, with a maximal rate for ATP and ADP hydrolysis in a pH range of 7.5-8.0 in the presence of Ca(2+) (5 mM). The enzyme displayed a maximal activity for ATP and ADP hydrolysis at 37 degrees C. It was able to hydrolyze purine and pyrimidine nucleosides 5'-di and triphosphates, being insensitive to classical ATPase inhibitors, such as ouabain (1 mM), N-ethylmaleimide (0.1 mM), orthovanadate (0.1 mM) and sodium azide (0.1 mM). A significant inhibition of ATP and ADP hydrolysis (68% and 34%, respectively) was observed in the presence of 20 mM sodium azide, used as a possible inhibitor of ATP diphosphohydrolase. Levamisole (1 mM) and tetramisole (1 mM), specific inhibitors of alkaline phosphatase and P1, P(5)-di (adenosine 5'-) pentaphosphate, an inhibitor of adenylate kinase did not alter the enzyme activity. The presence of a NTPDase in brain membranes of zebrafish may be important for the modulation of nucleotide and nucleoside levels, controlling their actions on specific purinoceptors in central nervous system of this specie.
Rico
Eduardo Pacheco
EP
Departamento de Ciências Fisiológicas, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul. Avenida Ipiranga 6681, 90619-900 RS, Porto Alegre, Brazil.
Senger
Mario Roberto
MR
Fauth
Maria da Graça
Mda G
Dias
Renato Dutra
RD
Bogo
Maurício Reis
MR
Bonan
Carla Denise
CD
D017766:Acid Anhydride Hydrolases / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D006868:Hydrolysis; D007425:Intracellular Membranes / Q000201:enzymology*; D043583:Nucleoside-Triphosphatase; D013379:Substrate Specificity; D015027:Zebrafish
D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D017766:Acid Anhydride Hydrolases; D043583:Nucleoside-Triphosphatase