Salivary proline-rich proteins

Abstract

Proline-rich proteins are major components of parotid and submandibular saliva in humans as well as other animals. They can be divided into acidic, basic and glycosylated proteins. The primary structure of the acidic proline-rich proteins is unique and shows that the proteins do not belong to any known family of proteins. The proline-rich proteins are apparently synthesized the acinar cells of the salivary glands and their phenotypic expression is under complex genetic control. The acidic proline-rich proteins will bind calcium with a strength which indicates that they may be important in maintaining the concentration of ionic calcium in saliva. Moreover they can inhibit formation of hydroxyapatite, whereby growth of hydroxyapatite crystals on the tooth surface in vivo may be avoided. Both of these activities as well as the binding site for hydroxyapatite are located in the N-terminal proline-poor part of the protein. Little is known about the functions of the glycosylated and basic proline-rich proteins.

Ileal amino acids digestibility of sorghum in weaned piglets and growing pigs

“…The low digestibility of proline and glycine could be attributable to the capacity of tannins to stimulate the synthesis of a proline-rich protein (Jansman, 1993;Haslam, 1998); this protein may be acidic, basic or glycosylated (Bennic, 1982), and may contain 40% proline and 20% glycine. It acts as the first line of defense against dietary tannins (Mehansho et al, 1985).…”

Basic proline‐rich proteins of murine parotid glands

“…The B-type polypeptide which lay outside the diagonal (p53"), and was designated B2'", had no equivalent in vitro product and hence it and its partner of identical pIdependent mobility may both result from B2 by post-translational processing in the parotid acinar cells. Differential proteolytic cleavage of precursors occurs amongst the human proline-rich protein family [13].…”

“…As proline-rich proteins in other mammalian species are components of saliva, where they are presumed to carry out their functions [13], we therefore studied the secretion of the basic isoprenaline-induced proline-rich proteins of the mouse and analysed saliva for their presence. Although isoprenaline acted in the long term (1 -10 days) as an inducer of prolinerich protein accumulation in mouse parotid glands (Fig.…”

“…Accompanying the morphological changes is an induction of members of the proline-rich protein family [7 -121 which are useful markers for 8-adrenergic action upon specific genes. Proline-rich proteins are classed into acidic and basic subgroups, are secreted into saliva [13] and in humans constitute 70% of total salivary protein [14].Proline-rich protein expression is different in rodents from that in humans. The proteins are present only in small amounts [9, 121 in normal rat parotid glands but are induced by isoprenaline to constitute 50% of total glandular protein [9, 101.…”

“…Accompanying the morphological changes is an induction of members of the proline-rich protein family [7 -121 which are useful markers for 8-adrenergic action upon specific genes. Proline-rich proteins are classed into acidic and basic subgroups, are secreted into saliva [13] and in humans constitute 70% of total salivary protein [14].…”