Kinetic characterization of ATP diphosphohydrolase and 5'-nucleotidase activities in cells cultured from submandibular salivary glands of rats.
The participation of ecto-ATP diphosphohydrolase (CD39; ecto-NTPDase) and ecto-5'-nucleotidase (CD73) activities in the nucleotide hydrolysis by salivary gland cells from rats was evaluated. We investigated the biochemical characteristics of these ectoenzymes in cells cultured from submandibular salivary glands of rats. The V(max) for the hydrolysis of ATP, ADP and AMP were 2275+/-153 (mean+/-SEM, n = 4), 941+/-96 (mean+/-SEM, n = 5) and 175+/-5 (mean+/-SEM, n = 5) nmol Pi liberated per min per mg of protein, respectively. The K(m) values for ATP, ADP and AMP were 224+/-8 microM (mean+/-SEM, n = 4), 163+/-15 microM (mean+/-SEM, n = 5) and 117+/-5 microM (mean+/-SEM, n = 5), respectively. The competition plot showed that ATP and ADP were hydrolyzed at the same active site on the enzyme. It may be postulated that the physiological role for this ecto-enzyme cascade is to terminate the action of the co-transmitter ATP, generating adenosine.
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Avenida Ramiro Barcelos 2600-Anexo, 90035-003, Porto Alegre, RS, Brazil.
Sandra Liana
SL
Henz
Cristiane Guimarães
CG
Ribeiro
Aline
A
Rosa
Rafael Augusto
RA
Chiarelli
Emerson André
EA
Casali
João José Freitas
JJ
Sarkis
D015720:5'-Nucleotidase / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001081:Apyrase / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D002412:Cations / Q000378:metabolism; D002478:Cells, Cultured; D006868:Hydrolysis; D007700:Kinetics; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013363:Submandibular Gland / Q000166:cytology* / Q000201:enzymology*; D013997:Time Factors
D002412:Cations; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D001081:Apyrase