Temperature sensitivity of the oxygenation reaction of stripped haemolysates from the freshwater fishes Lubeo capensis and Clarias gariepinus

ENGLISH ABSTRACT: The oxygen binding properties of haemoglobin solutions of the mudfish Labeo capensis and the catfish Clarias gariepinus, stripped by gel filtration chromatography and buffered at 23oC in 0,05 M Hepes (pH 7,48), were determined at 8oC, 15oC and 23oC. The P50 values obtained for L. capensis at these respective temperatures were 0,89 (pH7 ,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 means of a branchial organ which is absent in the mudfish. The purified hemolysate from C. gariepinus also displayed higher haem-haem co-operativity (n) at all three experimental temperatures compared to L. capensis. The heat of oxygenation (Δ H) between 8oC (pH 7 ,63) and 23oC (pH 7,49) calculated for L. capensis haemoglobin (- 56,3 kJ.mol-1 ) exceeded that of C. gariepinus (-43,1 kJ.mol-1). ************* AFRIKAANSE OPSOMMING: Die suurstofbindingseienskappe van hemoglobienoplossings van die moddervis Labeo capensis en die baber Clailas gariepinus, gesuiwer deur middel van jelfiltrasie-chromatografie en gebuffer by 23oC in 0,05 M Hepes (pH 7,48), is by 8oC, 15oC en 23oC vasgestel. Die P50-waardes vir L. capensis hemoglobien by hierdie temperature was onderskeidelik, 0,89 (pH7 ,63); 1,29 (pH 7,52) en 3,02 (pH 7,49) en vir C. gariepinus hemogtobien 2,47 (pH 7,61); 3,34 (pH 7,53) en 6,30 (pH 7,49). Die laer suurstofaffineit van C. gariepinus hemoglobien kan verband hou met die teenwoordigheid van 'n brangiale orgaan by hierdie vis en die feit dat babers verpligte lugasemhalers is. So 'n orgaan is afwesig by die moddervis. Die gesuiwerde hemolisaat van C. gariepinus vertoon, in vergelyking met die van L. capensis, ‘n groter mate van ko peratiwiteit (n) by al drie eksperimentele temperature. Die oksigeneringswarmte (ΔH), soos bereken tussen 8oC (pH 7,63) en 23oC (pH 7,49) is hoer vir L. capensis hemoglobien (- 56,3 kJ.mol-1 ) as vir C. gariepinu (-43,1 kJ.mol-1).