Propeptidi

Propeptidi are inactive precursor forms of peptides. They are synthesized as larger polypeptide chains that undergo post-translational modifications to become active peptides. This process typically involves proteolytic cleavage, where specific enzymes called proteases cleave the propeptide at defined sites, releasing the mature, functional peptide.

The propeptide sequence often plays a crucial role in the proper folding and transport of the precursor molecule within the cell. It can also act as a signal sequence, directing the propeptide and its associated peptide to a particular cellular compartment or for secretion. In some cases, the propeptide may also have regulatory functions, inhibiting the activity of the mature peptide until it is cleaved.

Examples of propeptidi are found in various biological systems. For instance, proinsulin is the precursor to insulin, a key hormone in glucose regulation. Proopiomelanocortin (POMC) is a large propeptide that gives rise to several biologically active peptides, including ACTH, MSH, and endorphins, which are involved in stress response, pigmentation, and pain perception. The cleavage of these propeptidi is a tightly regulated process essential for maintaining physiological homeostasis. Aberrant processing of propeptidi can lead to various diseases and disorders.