Catching sight of lysosomes

“All we wanted was to know something about the localization of glucose-6-phosphatase, which we thought might provide a possible clue to the mechanism of action, or lack of action, of insulin on the liver cell.” Thus begins Christian de Duve's discovery of lysosomes, which he first visualized in a 1956 paper in this journal (Novikoff et al., 1956).

Glucose-6-phosphatase was soon left behind when irregularities showed up with a control enzyme, acid phosphatase. After a gentle cell fractionation procedure, this activity was present at only one tenth of the level expected based on more violent extraction procedures. The activity then reappeared if extracts were left for several days in the refrigerator. As de Duve wrote, “…we could have rested satisfied with this result, dismissing the first series of assays as being due...