Proteolytic Effects on the Protochlorophyllide-Oxidoreductase in Oat

Abstract

The protochlorophyllide oxidoreductase (PCR) is one of the major intrinsic membrane proteins in etioplasts (Griffiths 1978, Apel et al. 1980, Röper et al. 1983). It catalyzes the first light-dependent step in chlorophyll biosynthesis. The enzyme activity is mainly found in PT-membranes of etioplasts, in comparison to PLBs (Lütz et al. 1981, Gerday et al. 1982), which holds also for PCR-protein (Ryberg and Sundqvist 1982, Lütz, in preparation). In case of etioplast membrane preparations from oat or bean plants, this enzyme is described as a 37/35 KD doublet in SDS-PAGE. It occurs as a single polypeptide (37 KD) in most other plants. However, Röper et al. (1983) could show, that for the oat membrane fractions the doublet is an isolation artefact, possibly due to internal protease activity in younger etioplasts. Bergweiler et al. (1983) demonstrated the appearance of the 35 KD band of the PCR during senescence of etiolated oat plants.