Proline Rich Protein 25 (PRR25)

Proline-rich proteins (PRPs) is a class of intrinsically unstructured proteins (IUP) containing several repeats of a short proline-rich sequence.Many tannin-consuming animals secrete a tannin-binding protein (mucin) in their saliva.

Tannin-binding capacity of salivary mucin is directly related to its proline content.Advantages in using salivary proline-rich proteins (PRPs) to inactivate tannins are :PRPs inactivate tannins to a greater extent than do dietary proteins; this results in reduced fecal nitrogen losses,PRPs contain non specific nitrogen and nonessential amino acids; this makes them more convenient for an animal to exploit rather than using up valuable dietary protein. Example of this class of protein is IB5, a human parotid salivary protein known to bind with polyphenols (binding responsible for the astringency mouth feel).