A study of permeability of lysosomes to amino acids and small peptides.

The latency of nitrocatechol sulphatase activity was measured in rat liver lysosomes before and after preincubation in 0.25m solutions of five amino acids, three dipeptides and a tripeptide. Rates of increase in ;free' activity were taken as an indication of rates of solute penetration into lysosomes and were correlated with the structure of each molecule studied. In general permeability was greater in solutions of pH7 than of pH5 or 6, and dipeptides entered more rapidly than amino acids or triglycine. The conclusions are in good agreement with those obtained by other methods.