Hemorphins, cytochrophins, and human beta-casomorphins bind to antiopiate (TYR-MIE-1) as well as opiate binding sites in rat brain.
Novel peptides with opiate activity, derived from endogenous sources (human and bovine casomorphins from milk, hemorphins from hemoglobin, and cytochrophins from mitochondrial cytochrome b), were tested for their ability to inhibit binding of the brain peptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) to its high affinity sites in rat brain. The order of potency in inhibiting binding of 125I-Tyr-MIF-1 was: hemorphin and bovine casomorphins greater than Tyr-MIF-1 greater than cytochrophins greater than human casomorphins. Naloxone and DAMGO were ineffective at inhibiting Tyr-MIF-1 binding. The results provide evidence that, in addition to their ability to bind to mu opiate receptors, these novel endogenous peptides with opiate activity and a peptide (Tyr-MIF-1) with antiopiate properties also bind to a non-opiate site labeled by Tyr-MIF-1. These sites could be involved in a balance between opiate and antiopiate peptides.
Zadina
J E
JE
VA Medical Center, New Orleans, LA.
Kastin
A J
AJ
Ge
L J
LJ
Brantl
V
V
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D004723:Endorphins / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats
D004723:Endorphins; D006454:Hemoglobins; D010446:Peptide Fragments; C036930:tyrosyl-prolyl-leucyl-glycinamide; C021968:beta-casomorphins; D009075:MSH Release-Inhibiting Hormone