Ribosomal peptide sequences are genetically coded, and they are synthesized at the endoplasmic reticulum by translation of mRNA. Often proteolysis generates the mature form. Ribosomal peptides function as hormones and signalling molecules.
Digested peptides are the result of nonspecific proteolysis as part of the digestive cycle.
Nonribosomal peptides are confined primarily to unicellular organisms, plants, and fungi. They are synthesized using a modular enzyme complex.