Prolactin-Induced Protein Human

Prolactin inducible protein (PIP) is a 17kDa glycoprotein existing in human seminal plasma. PIP is synthesized as a 146 amino acid long polypeptide exhibiting high sequence similarity with mouse submaxillary gland with a single glycosylation site. The precise biological functions of PIP are still ambiguous but various functions have been assigned to PIP due its existence at high concentration in biological fluids. PIP binds to various proteins such as fibrinogen, actin, keratin, myosin and tropomyosin. PIP is also expressed in pathological conditions of the mammary gland and in some exocrine tissues, such as the lacrimal, salivary and sweat glands. Due to PIP's association with secretory cell differentiation, it has been used in diagnostic evaluation of tumors of breast, salivary gland, and skin.