Casein has been documented to break down in the stomach to produce the peptide casomorphin (above stated that "Human digestion may break down casomorphins into inactive dipeptides by the enzyme dipeptidyl peptidase-4"), an opioid that acts as a histamine releaser.
They are from amino-terminus to carboxyl-terminus an Insulin-like growth factor binding domain, a kazal domain, a trypsin-like peptidase domain and a PDZ domain.
Latexin, a protein possessing inhibitory activity against rat carboxypeptidase A1 (CPA1) and CPA2 (MEROPS peptidase family M14A), is expressed in a neuronal subset in the cerebral cortex and cells in other neural and non-neural tissues of rat.
In the prostate it is present as an inactive pro-form which is activated through the action of KLK2, another kallikrein-related peptidase.