Kinetic characterization of adenosine deaminase activity in zebrafish ( Danio rerio) brain

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 2008-09, Vol.151 (1), p.96-101
• Main Authors: Rosemberg, Denis Broock, Rico, Eduardo Pacheco, Senger, Mario Roberto, Dias, Renato Dutra, Bogo, Maurício Reis, Bonan, Carla Denise, Souza, Diogo Onofre
• Format: Article
• Language: English
• Subjects: Adenine - analogs & derivatives; Adenine - pharmacology; Adenosine; Adenosine - metabolism; Adenosine deaminase; Adenosine Deaminase - metabolism; Adenosine Deaminase Inhibitors; Animals; Brain; Brain - cytology; Brain - enzymology; Cattle; Deamination; Hydrogen-Ion Concentration; Inosine; Kinetics; Membranes - metabolism; Metals - pharmacology; Solubility; Substrate Specificity; Temperature; Time Factors; Zebrafish; Zebrafish - metabolism
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/j.cbpb.2008.06.001

Adenosine deaminase (ADA; EC 3.5.4.4) activity is responsible for cleaving adenosine to inosine. In this study we described the biochemical properties of adenosine deamination in soluble and membrane fractions of zebrafish ( Danio rerio) brain. The optimum pH for ADA activity was in the range of 6.0–7.0 in soluble fraction and reached 5.0 in brain membranes. A decrease of 31.3% on adenosine deamination in membranes was observed in the presence of 5 mM Zn 2+, which was prevented by 5 mM EDTA. The apparent K m values for adenosine deamination were 0.22 ± 0.03 and 0.19 ± 0.04 mM for soluble and membrane fractions, respectively. The apparent V max value for soluble ADA activity was 12.3 ± 0.73 nmol NH 3 min − 1 mg − 1 of protein whereas V max value in brain membranes was 17.5 ± 0.51 nmol NH 3 min − 1 mg − 1 of protein. Adenosine and 2′-deoxyadenosine were deaminated in higher rates when compared to guanine nucleosides in both fractions. Furthermore, a significant inhibition on adenosine deamination in both soluble and membrane fractions was observed in the presence of 0.1 mM of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA). The presence of ADA activity in zebrafish brain may be important to regulate the adenosine/inosine levels in the CNS of this species.