The research proposed focuses on an apparent interaction between two chloroplast enzymes, an interaction that may play significant roles in regulation of carbon dioxide fixation in photosynthesis. The studies will assess whether interactions between one of these enymes and others in the reductive pentose-phosphate pathway occur; kinetic analyses and phase partition experiments, and effects of putative modulators will be employed to explore potential interactions. The findings will be pertinent to understanding regulation of key events in photosynthesis. The role of possible interactions between different enzymes involved in the chloroplast's metabolism of carbon dioxide during the latter's conversion to organic compounds will be examined in this research; an enlarged understanding of the regulation of carbon dioxide fixation in photosynthetic organisms should result.