Summary
Influence of some Factors on the Optimal pH of Ribonuclease from Cobra Snake Venom
Previously it was shown that Ribonuclease (RNase) from Viet Nam Cobra (Naja naja) venom is the unique true acidic enzyme expressing its high catalytic activity in an interval of pH from 1 to 4. In this study, pH-dependence of this enzyme was investigated in detail. It seemed that an optimum of pH of the enzyme in both crucial venom and chomatographically purified preparations varied in a wide interval of pH, with average value pHopt of 2.79 ± 0.32 and 2.14 ± 0.14 for RNase in lyophilized and fresh cobra venom respectively, whereas for the two constant chromatographic forms SK-2 and SK-3 pHopt is 2.50 ± 0.25 and 2.01 ± 0.23 respectively.
Moreover, the value of pHopt for cobra venom RNase can be changed in the dependence on concentrations of the enzyme and substrate. This variation in the pHopt value of the enzyme can be explained by existence of this RNase as an enzyme system composed of some interconvertible forms. It was demonstrated by dilution experiments that interconversion between these enzyme forms is very slow process: pHopt of RNase in the original enzyme solution is 2.23, at 6 hours after dilution of the enzyme solution, the value of pHopt of the enzyme will be 2.51.
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