What is proteolysis?

Proteolysis is the enzymatic cleavage of proteins and is carried out by proteases. It has a major impact in biology and medicine because it can lead to a context-dependent inactivation/activation of the protein, or uncover essential biologic activity.
Example: Important polypeptides like insulin and growth hormone, among hundreds of key molecules, are reliant on proteolysis for full functionality. However, excessive proteolysis in cartilage bone has a major role in osteoarthritis and osteoporosis. There are also a number of examples of proteolytic fragments that possess unforeseen biologic effects, such as on cancer angiogenesis and pain.

What is degradomics and how is it performed?

Degradomics is a term used to describe proteome-wide analysis of proteolysis, using mass spectrometry detection and sequencing of small peptides. The data output (degradome) comprises peptides of proteolytic origin from which cleavage sites are inferred and based on this, the proteases which generate these cleavages can be identified. It can be used in two ways:

• Forward degradomics is the unbiased uncovering of proteolytic cleavages in any biologic context, such as a disease tissue or cell culture.
• Reverse degradomics refers to the process by which the proteolytic activity specific to an individual protease is uncovered, i.e., by treating a proteome (protein library) of choice with the protease.

For both degradomics applications, we use a mass-spectrometry based strategy called terminomics, which seeks to identify protein termini. Since N-termini are more chemically reactive than C-termini, N-terminomics is more commonly used. A widely used N-terminomics method, which we employed here, is Terminal Amine Isotopic Labeling of Substrates, which was developed in the laboratory of Dr. Christopher Overall at the University of British Columbia.