What is the process of degradation of proteins into amino acids inside living cells?

Question

Just like beta oxidation does our cells have a distinct mechanism for degradation of proteins? There are processes for degradation of amino acids but where does these amino acids come from, is it all from dietary proteins? Are they not obtained from the proteins(enzymes) that are being continuously made inside the cells?

Answer 1

Cells have regulatory controls for their proteins through the ubiquitin-proteasome pathway and lysosomal proteolysis. In addition, cells have regulatory controls for the anabolism of proteins. The proteins that are degraded and synthesized are from throughout the cell. For synthesis, the amino acids come from the degraded proteins and the dietary proteins we consume. All of these mechanisms, both for the catabolism and anabolism of proteins, are governed by the genetic code.