roxidases (donor: hydrogen peroxide oxidoreductase; EC 1.11.1.7) from normal and mutant (makapuno)
coconut endosperms were compared in terms of their specific activities and isoenzyme patterns, physicochemical
properties and ability to oxidize IAA. Makapuno peroxidases have significantly higher activity during the early stages of
development and significantly lower activity at maturity when compared with the normal. Six anodic isoenzymes were
detected at pH 8.9 from both sources by polyacrylamide gel electrophoresis. Both normal and makapuno crude
peroxidases have optimum activity at pH 5.5 and are thermostable over a wide range of temperature. The V,, was
obtained at 1 x 10e2 M hydrogen peroxide while the apparent K, was at ca 1 x lo-” M hydrogen peroxide. In general,
no marked difference was noted between the physicochemical properties of peroxidases from both sources. Isolation
and partial purification of the isoenzymes were performed by conventional methods including ammonium sulfate
fractionation, DEAE Sephadex A-SO ion exchange chromatography and Sephadex G-200 gel filtration. Peroxidase
activity was localized in the Xl-95 % ammonium sulfate precipitate. Gel filtration resolved three protein peaks with
peroxidase (Px) activity, the electrophoretic mobilities of which corresponded to Px3, Px4 and Px5. Px5 was purified
17 600-fold and found to be a tetramer with a native MW of 196000 and a subunit MW of 55 000. Px3 and Px4 were
monomers with MWs of 36 300 and 46 800, respectively. IAA oxidase activity was detected in the partially purified
peroxidases from developing normal endosperms but not from mature endosperms.
roxidases (donor: hydrogen peroxide oxidoreductase; EC 1.11.1.7) from normal and mutant (makapuno)coconut endosperms were compared in terms of their specific activities and isoenzyme patterns, physicochemicalproperties and ability to oxidize IAA. Makapuno peroxidases have significantly higher activity during the early stages ofdevelopment and significantly lower activity at maturity when compared with the normal. Six anodic isoenzymes weredetected at pH 8.9 from both sources by polyacrylamide gel electrophoresis. Both normal and makapuno crudeperoxidases have optimum activity at pH 5.5 and are thermostable over a wide range of temperature. The V,, wasobtained at 1 x 10e2 M hydrogen peroxide while the apparent K, was at ca 1 x lo-” M hydrogen peroxide. In general,no marked difference was noted between the physicochemical properties of peroxidases from both sources. Isolationand partial purification of the isoenzymes were performed by conventional methods including ammonium sulfatefractionation, DEAE Sephadex A-SO ion exchange chromatography and Sephadex G-200 gel filtration. Peroxidaseactivity was localized in the Xl-95 % ammonium sulfate precipitate. Gel filtration resolved three protein peaks withperoxidase (Px) activity, the electrophoretic mobilities of which corresponded to Px3, Px4 and Px5. Px5 was purified17 600-fold and found to be a tetramer with a native MW of 196000 and a subunit MW of 55 000. Px3 and Px4 weremonomers with MWs of 36 300 and 46 800, respectively. IAA oxidase activity was detected in the partially purifiedperoxidases from developing normal endosperms but not from mature endosperms.
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