Soluble NTPDase: An additional system of nucleotide hydrolysis in rat blood serum.
The participation of a nucleoside triphosphate diphosphohydrolase in the nucleotide hydrolysis by rat blood serum was evaluated. Nucleoside triphosphate diphosphohydrolase and phosphodiesterase are enzymes possibly involved in ATP and ADP hydrolysis. The specific activity of the phosphodiesterase activity (using thymidine 5'-monophosphate p-nitrophenyl ester as substrate) was 4.92 +/- 0.73 (mean +/- SD, n = 10) nmol p-nitrophenol.min(-1).mg(-1) protein and the specific activities for ATP and ADP were 1.31 +/- 0.37 (mean +/- SD, n = 7) and 1.36 +/- 0.25 (mean +/- SD, n = 5) nmol Pi.min(-1).mg(-1) protein, respectively. A competition plot demonstrated that ATP and ADP hydrolysis occurs at the same active site. The effect of suramin and phenylalanine on ATP, ADP and thymidine 5'-monophosphate p-nitrophenyl ester hydrolysis was investigated. The results were opposite considering the hydrolysis of ATP and ADP and that of the substrate marker for the enzyme phosphodiesterase. These results are indicative of the presence of, at least, two enzymes participating in the serum nucleotide hydrolysis. The presence of cAMP did not affect the hydrolysis velocity of ATP and ADP, while thymidine 5'-monophosphate p-nitrophenyl ester hydrolysis was inhibited by cAMP by approximately 47%, suggesting that the hydrolysis of the ATP and ADP, under our assay conditions, occurs at a different site from the phosphodiesterase site. Both enzyme activities, in the rat blood serum, may be involved in the modulation of the nucleotide/nucleoside ratio in the circulation, serving an in vivo homeostatic and antithrombotic function. In addition, the phosphodiesterase may act on DNA or RNA liberated upon tissue injury and/or cell death.
Oses
Jean Pierre
JP
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Cardoso
Cássia Maria
CM
Germano
Renata Albuquerque
RA
Kirst
Inajara Barreto
IB
Rücker
Bárbara
B
Fürstenau
Cristina Ribas
CR
Wink
Márcia Rosângela
MR
Bonan
Carla Denise
CD
Battastini
Ana Maria Oliveira
AM
Sarkis
João José Freitas
JJ
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD; D001081:Apyrase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006868:Hydrolysis; D008297:Male; D009711:Nucleotides / Q000097:blood* / Q000378:metabolism; D043264:Phosphodiesterase I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility
D015703:Antigens, CD; D004791:Enzyme Inhibitors; D009711:Nucleotides; D043264:Phosphodiesterase I; D000251:Adenosine Triphosphatases; C027201:ectoATPase; D001081:Apyrase; C067869:CD39 antigen