Differential distribution of chlorophyll biosynthetic intermediates in stroma, envelope and thylakoid membranes in Beta vulgaris.

Stroma, envelope and thylakoid membranes were prepared from chloroplasts isolated from leaves of Beta vulgaris. Out of total plastidic protochlorophyllide, envelope membranes contained 1.5%, thylakoids had the maximum 98.48% and stroma had a trace fraction of 0.02%. Distribution of the Mg-protoporphyrin IX and its monoester was 89.0% in thylakoids, 10.0% in stroma and 1.0% in envelope. A substantial fraction (33.77%) of plastidic protoporphyrin IX was partitioned into stroma. Envelope contained 0.66% and thylakoids had 65.57% of the total plastidic protoporphyrin IX pool. The proportion of monovinyl and divinyl forms of protochlorophyllide was almost similar in intact plastid, thylakoids, and outer and inner envelope membranes suggesting a tight regulation of vinyl reductase enzyme. The significance of differential distribution of chlorophyll biosynthetic intermediates among thylakoids, envelope and stroma is discussed.

Detection of protoporphyrin IX in envelope membranes of pea chloroplasts.

Envelope membranes were prepared from mature pea chloroplasts. The tetrapyrrole contents of envelope membranes were analysed. The envelope membranes of pea chloroplasts contained substantial amounts of protoporphyrin IX and trace amounts of Mg-protoporphyrin IX and its monoester in addition to protochlorophyllide. The protoporphyrin IX content of envelope membranes was 89.25 pmol (mg protein)(-1). Its content in pea envelope membrane was higher than that of protochlorophyllide. The proportion of monovinyl and divinyl forms of protochlorophyllide present in pea chloroplast envelope membrane was 3:7. The significance of the presence of protoporphyrin IX in the envelope membrane is discussed in relation to plastidic Chl biosynthesis.