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  • Title: The proteolytic degradation in vitro of the NADPH-protochlorophyllide oxidoreductase of barley (Hordeum vulgare L.).
    Author: Häuser I, Dehesh K, Apel K.
    Journal: Arch Biochem Biophys; 1984 Feb 01; 228(2):577-86. PubMed ID: 6696447.
    Abstract:
    A cell-free membrane system has been developed from isolated barley etioplasts which displays a highly selective decrease of the NADPH-protochlorophyllide oxidoreductase in vitro which is indistinguishable from that observed previously in the intact plant. The rapid breakdown of the enzyme protein in vitro is caused by a membrane-bound proteolytic activity. The protease is essentially independent of pH in the physiological pH range of 6 to 8.5. The optimum temperature for the reaction is approximately 40 degrees C. In the presence of excessive protochlorophyllide the enzyme is no longer degraded or inactivated during illumination of dark-grown plants. In the isolated membrane fraction protochlorophyllide also enhances the stability of the enzyme, a similar effect is exerted by NADPH but not by NADH. The results suggest that the inactivation of the NADPH-protochlorophyllide oxidoreductase is influenced by the interaction of the enzyme with protochlorophyllide and NADPH. In the absence of these two components the enzyme becomes susceptible to proteolytic degradation.
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