Peptide hormone metabolism

Insulin processing occurs in 4 steps: formation of intramolecular disulfide bonds, formation of proinsulin-zinc-calcium complexes, proteolytic cleavage of proinsulin by PCSK1 (PC1/3) and PCSK2 to yield insulin, translocation of the granules across the cytosol to the plasma membrane.

During Synthesis, secretion, and deacetylation of Ghrelin, proghrelin is acylated by ghrelin O-acyltransferase and cleaved by PCSK1 to yield the mature acyl ghrelin and C-ghrelin. In the bloodstream acyl ghrelin is deacylated by butyrylcholinesterase and platelet-activating factor acetylhydrolase.

During Metabolism of Angiotensinogen to Angiotensin, Renin cleaves angiotensinogen to yield a decapaptide, angiotensin I (angiotensin-1, angiotensin-(1-10)). Two C-terminal amino acid residues of angiotensin I are then removed by angiotensin-converting enzyme (ACE), located on the surface of endothelial cells, to yield angiotensin II (angiotensin-2, angiotensin-(1-8)), the active peptide that causes vasoconstriction, resorption of sodium and chloride, excretion of potassium, water retention, and aldosterone secretion. More recently other, more tissue-localized pathways leading to angiotensin II and alternative derivatives of angiotensinogen have been identified and described.

Incretin synthesis, secretion, and inactivation occurs through processing of incretin precursors (preproGLP-1 and preproGIP) by PCSK1. After secretion both incretins (GLP-1 and GIP) can be inactivated by cleavage by DPP4.

Peptide hormone biosynthesis describes processing of glycoprotein hormones (those which include carbohydrate side-chains) and corticotropin.