Effects of pronase on isolated chloroplasts

Subjecting isolated spinach chloroplasts to mild proteolysis (10-minute incubation at 20 C in 500 micrograms per milliliter pronase) caused chloroplast clumping but did not affect their integrity as measured by their ability to carry out light stimulated, glycerate-3-P-dependent O₂ evolution. Transmission electron microscopy revealed no detectable differences between the control and treated plastids. Mild proteolysis inactivated exogenously added pyruvate kinase and should be a useful technique in certain enzyme distribution studies.