Antibody inhibition of external aldolase activity in spinach chloroplast preparations.

Antibodies (rabbit) have been prepared against total stroma from isolated spinach (Spinacia oleracea L. cv. Viking II) chloroplasts. These antibodies inhibited most of the aldolase activity present outside the chloroplasts in preparations of intact (80-95%) chloroplasts. They also reduced the amount of labelled fructose-1,6-bisphosphate found in the medium after 14CO2 fixation with such preparations. Both intact and broken chloroplasts were strongly agglutinated by the antibodies. The results indicate that the external fructose-1,6-bisphosphate was formed from excreted dihydroxyacetone phosphate by the action of aldolase and those phosphate isomerase present outside the chloroplasts. The contamination of organelle preparations with free enzymes or enzymes adsorbed on the outer surface of the organelles is probably a general phenomenon. It is suggested that antibodies can he used as a tool to detect and selectively inhibit such contaminating enzyme activities. [ABSTRACT FROM AUTHOR]