Rubiscolin-6, a delta opioid peptide derived from spinach Rubisco, has anxiolytic effect via activating sigma1 and dopamine D1 receptors.

Rubiscolin-6 (Tyr-Pro-Leu-Asp-Leu-Phe) is a delta opioid peptide derived from the large subunit of spinach d-ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). We previously reported that rubiscolin-6 had an analgesic effect and stimulated memory consolidation. Here we show that intraperitoneally (i.

beta-Lactotensin, a neurotensin agonist peptide derived from bovine beta-lactoglobulin, enhances memory consolidation in mice.

beta-Lactotensin (His-Ile-Arg-Leu) is an ileum-contracting tetrapeptide isolated from bovine beta-lactoglobulin. We previously reported that a neurotensin agonist beta-lactotensin shows antinociceptive effect through neurotensin NT(2) receptor. We found that centrally or orally administered beta-lactotensin at a dose of 60nmol/mouse or 300-500mg/kg, respectively, increased memory consolidation in the step-through-type inhibitory avoidance test in mice.

Enterostatin (APGPR) enhances memory consolidation in mice.

Enterostatin (APGPR) is a pentapeptide released from its precursor protein, procolipase. We found for the first time that enterostatin has memory-enhancing activity. Enterostatin enhanced memory consolidation after central or oral administration at a dose of 10 nmol/mouse or 300 mg/kg, respectively, in a step-through type passive avoidance test in mice.

Antinociception induced by beta-lactotensin, a neurotensin agonist peptide derived from beta-lactoglobulin, is mediated by NT2 and D1 receptors.

In this study, we examined the antinociceptive effect of beta-lactotensin, a neurotensin agonist that has been isolated from the chymotrypsin digest of beta-lactoglobulin as an ileum-contracting peptide. Beta-lactotensin showed naloxone-insensitive antinociceptive activity by the tail-pinch test after i.c.

Structure-activity relationship of rubiscolins as delta opioid peptides.

To study the structure-activity relationship of rubiscolins (YPLDLF and YPLDL), delta opioid peptides derived from the spinach Rubisco, we substituted the amino acid residues and evaluated their activities by mouse vas deferens (MVD) and guinea pig ileum (GPI) assays as well as receptor affinity. Replacement of Leu(3) with Ile and Met in rubiscolin-6 potentiated the delta opioid activity by about four times in MVD assay. Asp(4) cannot be replaced by Ala, Glu or His.