Guanine and adenine nucleotidase activities in rat cerebrospinal fluid.
Adenine and guanine nucleotides have been shown to exert multiple roles in central and peripheral nervous systems, and the sequential breakdown of these nucleotides by enzymatic systems is an important step in the modulation of their extracellular effects. The aim of this study was to investigate whether nucleotide hydrolysis also occurs in the cerebrospinal fluid (CSF) of rats. CSF was able to hydrolyze all guanine and adenine nucleotides investigated (2.0 mM): GDPz.Gt;ADP=ATP=GTPz.Gt;AMP=GMP. More detailed studies with the diphosphate nucleotides showed that the hydrolysis of ADP and GDP was linear with incubation time and protein concentration. The apparent K(M) (Henry-Michaelis-Menten constant) and V (maximal velocity) values for ADP and GDP were 164.3+/-54.7 microM and 12.2+/-3.8 nmol P(i)/min per mg protein, and 841.0+/-90.2 microM and 22.8+/-8.0 nmol P(i)/min per mg protein. The sum of ADP, GDP and UDP hydrolysis (2.0 mM) upon individual incubations with CSF was similar to the hydrolysis observed when all three nucleotides were incubated together. This pattern of hydrolysis strongly suggests the involvement of more than one enzyme activity. The higher maximum activity for GDP and UDP compared to ADP is compatible with presence of a soluble NTDPase5.
Cruz Portela
Luis Valmor
LV
Departamento de Bioqui;mica, ICBS, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600, anexo, 90035-003, RS, Porto Alegre, Brazil.
Oses
Jean Pierre
JP
Silveira
André Luiz
AL
Schmidt
André Prato
AP
Lara
Diogo Rizzato
DR
Oliveira Battastini
Ana Maria
AM
Ramirez
Galo
G
Vinadé
Lúcia
L
Freitas Sarkis
João José
JJ
Souza
Diogo Onofre
DO
D000227:Adenine Nucleotides / Q000134:cerebrospinal fluid* / Q000378:metabolism; D000818:Animals; D005260:Female; D006150:Guanine Nucleotides / Q000134:cerebrospinal fluid* / Q000378:metabolism; D006868:Hydrolysis; D009708:Nucleotidases / Q000134:cerebrospinal fluid* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D000227:Adenine Nucleotides; D006150:Guanine Nucleotides; D009708:Nucleotidases; C030287:nucleotidase