Protein degradation in vivo and its regulation.

Protein degradation in mammalian cells may be regulated by size of the polypeptide subunit, susceptibility to degradation by proteases, alteration by mutational changes, and interaction with various ligands, including other proteins, lipids, cofactors, or metabolic intermediates. The pathway of degradation is not defined but appears to involve both lysosomal and nonlysosomal proteases.