초록

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Abstract ▼ AI-Helper

Two anodic isoperoxidases, named isoperoxidase $A_3$ and $A_4$, were isolated from tobacco callus line, Nicotiana tabaccum L., var. Virginia 115. Isolation of the enzymes was accomplished using DEAE-cellulose ion exchange chromatography and Sephadex G-150 gel filtration. The mo...

Two anodic isoperoxidases, named isoperoxidase $A_3$ and $A_4$, were isolated from tobacco callus line, Nicotiana tabaccum L., var. Virginia 115. Isolation of the enzymes was accomplished using DEAE-cellulose ion exchange chromatography and Sephadex G-150 gel filtration. The molecular weight of isoperoxidase $A_3$ was approximately 38,000 as determined by SDS polyacrylamide gel electrophoresis and 38,500 estimated with Sephadex G-150 gel filtration. The molecular weight of isoperoxidase $A_4$ was 43,000 as determined by SDS polyacrylamide gel electrophoresis and Sephadex G-150 gel filtration. The optimum pHs for guaiacol with isoperoxidase $A_3$ and $A_4$ were pH 6.0 and pH 7.0, respectively, and these two isoperoxidases had same $K_m$ value of 5 mM for guaiacol. Substrate studies with natural phenolic compounds such as scopoletin, esculetin, ferulic acid and chlorogenic acid were performed and the $K_m$ values for these substrates were 0.18 mM, 0.24 mM, 0.26 mM and 0.35 mM, respectively, in case of isoperoxidase $A_3$. Such $K_m$ values did not differ greatly from those of isoperoxidase $A_4$ from Virginia strain and known scopoletin peroxidase $A_f$ from WR-132 strain. In comparison with isoperoxidase $A_3$ from W-38 strain and $A_f$ from WR-132 strain which were known as scopoleticn peroxidases, these two enzymes from Virginia strain showed notable differences in scopoletin oxidizing ability in terms of relative substrate oxidation ratios.