Biosyntheses and processing of lysosomal cysteine proteinases in rat macrophages

Abstract
The intracellular processing and release of three lysosomal cysteine proteinases, cathepsin B, H and L, by rat peritoneal macrophages were investigated by pulse‐chase experiments. Newly synthesized procathepsins B (39 kDa), H(41 kDa) and L (39 kDa) after 15 min labeling were processed to the mature, single‐chain enzymes within 1 h. The single‐chain forms of cathepsin B, H and L were further processed to two‐chain forms at different rates: conversion of cathepsin L to the two‐chain form was rapid, whereas the conversions cathepsin B and H took at least 6 h. Macrophages released 30% of the procathepsins B and L, and 10% of the procathepsin H.