The role of lysosomal enzymes in skeletal tissues.

The presence of digestive enzymes within cells has been known for a long time, but it was not until de Duve and his co-workers investigated the intracellular localisation of these enzymes that it was realised that a variety of acid hydrolases coexisted within a distinctive organelle (for review see de Duve 1969). This organelle, named the “lysosome” by the Louvain workers, is now known to be part of a vacuolar system present in all but the most highly specialised cells (the exceptions being the mature erythrocyte and the spermatozoon). The relevance of the lysosomal system to the physiology and pathology of skeletal tissues was first investigated at the Strangeways Laboratory. Work in this and in many other laboratories has now led to a confirmation of a role of lysosomes in joint tissues, though we are, as yet, far from an understanding of the full complexities of their function in these tissues. This article will deal briefly with some of the properties of lysosomes and their constituent enzymes in the context of recent studies on the turnover of skeletal tissue macromolecules.