Cathepsins, glycosaminoglycans and biological role of their interactions

Abstract

Cathepsins are protein-degrading enzymes that can be found in many living organisms. Most of them are cysteine proteases but are also cathepsins A and G which are serine proteases or cathepsins D and E which are aspartyl proteases. To date we know that there are 15 members of this family with most of their structures experimentally available. Regardless differences in their aminoacid sequences cathepsins share the same secondary structure pattern which is reflected in the same fold. Cathepsins play a vital role in diverse of biological processes such as bone resorption, intracellular proteolysis and regulation of programmed cell death. Changes in their activity in organism may lead to many serious diseases, either to pycnodysostosis in case of deficiency or to osteoporosis in case of excessive activity. However, enzymatic activity of the cathepsins can be moderated by glycosaminoglycans – a group of linear, periodic, negatively charged carbohydrates.