Biosynthesis and secretion of milk proteins: a review.

Recent years have seen a great increase in the knowledge and understanding of milk proteins. Arising from several origins including the blood stream and various cellular sources, many of the proteins found in milk are products of the secretory cells directly involved in the synthesis and secretion processes of various milk components. The lactation-specific proteins present in major amounts are synthesized in the rough endoplasmic reticulum (RER) under genetic control and undergo further post-translational modifications in their secretory route from the RER through the Golgi apparatus and secretory vesicles before ejection into the lumen with other milk components. Various molecular aspects of these mechanisms and their control are now understood, but many remain to be described.