Catalase was isolated in a pure form from sweet potato root microbodies by simple procedures including ammonium sulfate fractionation and Sepharose 6B column chromatography. A single protein band was detected after polyacrylamide gel electrophoresis of the purified preparation. The catalase consisted of polypeptides with a molecular weight of 60,000 when analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis, while the molecular weight of the enzyme was about 240,000 when estimated from sucrose density gradient centrifugation. The enzyme's ratio of absorbance at 280 nm to that at 405 nm was about twice that of mammalian catalase. The catalase showed a maximal activity at pH 6.5–8.5 but was stable only at alkaline pHs. In double immunodiffusion tests, antiserum against the purified preparation formed a single precipitin line with the crude soluble fraction from sweet potato root tissue as well as with the purified preparation. The antiserum had no ability to inhibit the activity, but catalase in both the crude fraction and the purified preparation was completely precipitated by the antiserum.
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Esaka et al. (1982) studied this question.