TEMPERATURE SENSITIVITY OF THE OXYGENATION REACTION OF STRIPPED HEMOLYSATES FROM THE FRESH-WATER FISHES LABEO-CAPENSIS AND CLARIAS-GARIEPINUS

The oxygen binding properties of haemoglobin solutions of the mudfish Labeo capensis and the catfish Clarias gariepinus, stripped by gel fil tration chromatography and buffered at 23-degrees-C in 0,05 M Hepes (p H 7,48), were determined at 8-degrees-C, 15-degrees-C and 23-degrees-C . The P50 values obtained for L. capensis at these respective temperat ures were 0,89 (pH 7,63); 1,29 (pH 7,52) and 3,02 (pH 7,49) and those for C. gariepinus haemoglobin were 2,47 (pH 7,61); 3,34 (pH 7,53) and 6,30 (pH 7,49). The lower oxygen affinity of C. gariepinus haemoglobin may be related to the obligatory air breathing of C. gariepinus by me ans of a branchial organ which is absent in the mudfish. The purified hemolysate from C. gariepinus also displayed higher haem-haem co-opera tivity (n) at all three experimental temperatures compared to L. capen sis. The heat of oxygenation (DELTAH) between 8-degrees-C (pH 7,63) an d 23-degrees-C (pH 7,49) calculated for L. capensis haemoglobin (-56,3 kJ.mol-1) exceeded that of C. gariepinus (-43,1 kJ.mol-1).