Peptide hormones for defense, growth, development and reproduction

Abstract

Peptide hormones are extracellular signaling molecules that are commonly found in animals and plants (38). A broad spectrum of physiological processes are regulated by peptide signals including metabolism, cell division, growth, pain, well being, reproduction and immunity, as examples. The first peptide hormone, insulin, was isolated in 1921 (1), which led to the isolation of hundreds of peptide signals from animals and, more recently, to their isolation from plants (34). The majority of our fundamental knowledge about peptide signals has been from studies in animals, where peptide hormones are synthesized through the secretory pathway and are derived from larger precursor proteins by proteolytic processing enzymes. Two general classes of peptide hormones are found in animals, endocrine hormones (10) and membrane-anchored cytokines and growth factors (21).