Dye-sensitized photo-oxidation of acid ribonuclease from pea cotyledons |
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| Authors: | Paul S. Phillips John A. Bryant Hilary J. Smyth |
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| Affiliation: | 1. Department of Chemistry, University College, P.O. Box 78, Cardiff, CF1 1XL, U.K.;2. Department of Plant Science, University College, P.O. Box 78, Cardiff, CF1 1XL, U.K. |
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| Abstract: | In crude extracts, pea cotyledon acid ribonuclease is not inactivated by photo-oxidation, but after 150-fold purification, it is markedly inactivated when illuminated in the presence of methylene blue at pH 7.2. It is, however, still resistant to methylene blue-sensitized photo-oxidation at pH 5.4. These data suggest that photo-oxidation of methionine, cysteine and tryptophan has no effect on enzyme activity, whereas photo-oxidation of histidine markedly reduces catalytic acitivity. It is thus likely that the mode of action of acid ribonuclease from pea cotyledons is similar to that of pancreatic ribonuclease. |
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| Keywords: | Leguminosae pea photo-oxidation ribonuclease, histidine. |
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