New Pituitary Peptide Relationships

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Abstract
A glycoprotein molecule discovered in pituitary glands of experimental animals is thought to be the precursor molecule for the pituitary peptides ACTH and beta-lipotropin, molecules themselves known to contain the amino acid sequences of several smaller peptides subsequently isolated. Evidence now exists to suggest the enzymatic cleavage of ACTH to alpha-MSH and corticotropic-like intermediate lobe peptide (CLIP), pituitary peptides with effects upon the fetal pituitary gland. Beta-lipotropin is probable the prohormone for the peptides beta-MSH, gamma-lipotropin, methionine-enkephalin, and beta-endorphin. Beta-MSH may enchance the known physiologic effects of mammalian central nervous system transmitters, while the enkephalins and beta-endorphin have been shown to exhibit opioid analgesic properties as well as effects upon behavior, temperature regulation, and the release of growth hormone and prolactin. Homologies among their amino acid sequences and evidence for prohormone activity in ACTH, beta-lipotropin, and the putative ACTH-beta lipotropin precursor suggest the possibility of the presence of a previously unsuspected interrelationship in the synthesis and release of these various pituitary peptides.

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