Identification of the Main Species of Tetrapyrrolic Pigments in Envelope Membranes from Spinach Chloroplasts

The chlorophyll precursors protochlorophyllide and chlorophyllide were identified in purified envelope membranes from spinach (Spinacia oleracea) chloroplasts. This was shown after pigment separation by high performance liquid chromatography (HPLC) using specific fluorescence detection for these compounds. Protochlorophyllide and chlorophyllide concentrations in envelope membranes were in the range of 0.1 to 1.5 nmol/mg protein. Chlorophyll content of the envelope membranes was extremely low (0.3 nmol chlorophyll a/mg protein), but the molar ratios of protochlorophyllide and chlorophyllide to chlorophyll were 100 to 1000 times higher in envelope membranes than in thylakoid membranes. Therefore, envelope tetrapyrrolic pigments consist in large part (approximately one-half) of nonphytylated molecules, whereas only 0.1% of the pigments in thylakoids are nonphytylated molecules. Clear-cut separation of protochlorophyllide and chlorophyllide by HPLC allowed us to confirm the presence of a slight protochlorophyllide reductase activity in isolated envelope membranes from fully developed spinach chloroplasts. The enzyme was active only when envelope membranes were illuminated in the presence of NADPH.