LOCALIZATION OF FERROCHELATASE ACTIVITY WITHIN MATURE PEA-CHLOROPLASTS

Precise localization within the chloroplast of the membrane-bound enzy mes involved in heme and chlorophyll biosynthetic pathways is of centr al importance for better understanding the regulation of the carbon fl ow into these two pathways. In this study we examine the localization of ferrochelatase activity within mature pea chloroplasts. Our results provide evidence that chloroplast ferrochelatase is associated only w ith thylakoid membranes. The presence of ferrochelatase in chloroplast thylakoids emphasizes the role of this membrane system in chloroplast protoheme biosynthesis. Furthermore, these results raise the possibil ity that heme and chlorophyll biosynthesis are compartmentalized in tw o distinct membrane systems within mature chloroplasts.