The activity of methaemoglobin reductase in toadfish (Halobatrachus didactylus) and gilt head sea bream (Sparus aurata)

Aníbal, J.; Bicho, M.

http://hdl.handle.net/10400.1/2773

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Authors

Aníbal, J.

Bicho, M.

Abstract(s)

The erythrocytes intracellular oxidative stress oxidizes the haemoglobin forming methaemoglobin, which is nonfunctional. To oppose this formation fishes have an enzyme that reverses the process called methaemoglobin reductase. In vitro activity of the methaemoglobin reductase was determined in two marine fishes with different habitats and behaviours (Halobatrachus didactylus and Sparus aurata). The KM and Vmax, were determined through the Eisenthal and Cornish-Bowden Plot. The basis for this study is that the methaemoglobin reductase system has very active ferricyanide reductase activity, using NADH as the electrons donor. Halobatrachus didactylus showed higher values of methaemoglobin reductase activity (38.9 mmol NAD+/min/gHb) than Sparus aurata (27.8 mmol NAD+/min/gHb). The reductase of Halobatrachus didactylus had, for both substrates, higher values of KM (potassium ferricyanide: 0.133 mM, NADH: 0.067 mM) and lower values of Vmax (potassium ferricyanide: 0.097 min-1; NADH: 0.025 min-1), than Sparus aurata (potassium ferricyanide: KM=0.092 mM, Vmax=0.176 min-1, NADH: KM=0.032 mM, Vmax=0.062 min-1). The results indicated that Halobatrachus didactylus’s methaemoglobin reductase had high antioxidant efficiency, although that one of the Sparus aurata had more sensitivity to the presence of low concentrations of methaemoglobin. The meaning of this different behaviour, at the moment can not be envisaged.

URI

http://hdl.handle.net/10400.1/2773

Citation

Aníbal, J.; Bicho, M. The activity of methaemoglobin reductase in toadfish (Halobatrachus didactylus) and gilt head sea bream (Sparus aurata), Trabalho apresentado em VII International Symposium on Fish Physiology, In VII International Symposium on Fish Physiology, Oslo, Norway, 1996.