Opiate binding properties of naturally occurring N- and C-terminus modified beta-endorphins.
Beta-endorphin is further processed within the pituitary and brain by either N-terminal acetylation, carboxy-terminal proteolysis, or both. These naturally occurring analogues are stored intracellularly and, in some tissues, represent the majority of beta-endorphin immunoreactivity detected by antisera. It is therefore critical to determine their relative potencies at the opiate receptor. This study demonstrates that cleavage of the C-terminus tetrapeptide brings about a 10-fold decrease in opiate binding potency of either camel or human beta-endorphin. N-Acetylation, on the other hand, causes over a thousand fold loss in opiate potency rendering the peptide effectively inactive. Since unmodified beta-endorphin is approximately equipotent at multiple opiate receptors, we tested for possible differential shifts towards mu or delta-type receptors which may result from the modification. Our results show no change in selectivity, but simply an overall loss of potency.
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D004723:Endorphins / Q000378:metabolism*; D066298:In Vitro Techniques; D008566:Membranes / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D001615:beta-Endorphin
D004723:Endorphins; D010446:Peptide Fragments; D011957:Receptors, Opioid; D001615:beta-Endorphin