Yunden Jinsmaa

Enzymatic release of neocasomorphin and β-casomorphin from bovine β-casein

Abstract Conditions for the release of β-casomorphin-7 from bovine β-casein by gastrointestinal proteases in vitro were investigated. β-Casomorphin-7 was released only from a genetic variant of β-casein containing a His residue at the 67th position of the peptide chain. Elastase cleaved the peptide bond between Ile 66 and His 67 , releasing the carboxyl terminus of β-casomorphin-7. Pepsin and leucine aminopeptidase were required to release the amino terminus of this peptide. β-Casomorphin-9, -13, and -21 also were isolated, and their opioid activities were measured. In this study, we also isolated a novel opioid peptide neocasomorphin-6 (Tyr-Pro-Val-Glu-Pro-Phe), which was released by action of trypsin or pepsin and chymotrypsin.

Release of opioid peptides, gluten exorphins by the action of pancreatic elastase

The release of opioid peptides, gluten exorphins A, which have been isolated from the pepsin–thermolysin digest of wheat gluten, with gastrointestinal proteases was examined. High levels of gluten exorphin A5 (Gly–Tyr–Tyr–Pro–Thr) immunoreactive materials were detected in the pepsin–pancreatic elastase digest by a competitive ELISA. From this digest, gluten exorphin A5, B5 and B4 were isolated. This means that these peptides are released in the gastrointestinal tracts after ingestion of wheat gluten. The yield of gluten exorphin A5 in the pepsin–elastase digest was larger than that in the pepsin–thermolysin digest. The gluten exorphin A5 sequence is found 15 times in the primary structure of the high molecular weight glutenin. The region from which gluten exorphin A5 was released by the action of pancreatic elastase was identified using synthetic fragment peptides.

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

Abstract In this study, we examined the antinociceptive effect of β-lactotensin, a neurotensin agonist that has been isolated from the chymotrypsin digest of β-lactoglobulin as an ileum-contracting peptide. β-Lactotensin showed naloxone-insensitive antinociceptive activity by the tail-pinch test after i.c.v. (200 nmol/mouse) or s.c. (300 mg/kg) administration in ddY mice. Tolerance was not developed to antinociception induced by β-lactotensin after repeated s.c. administration for 5 days. The antinociceptive activity of β-lactotensin was blocked by treatment with the neurotensin NT2 receptor antisense ODN, while treatment with the NT1 receptor antisense ODN had no effect. The antinociceptive activity was also blocked by a dopamine D1 receptor antagonist, SCH23390 (1 μg/mouse, i.c.v.), while a D2 receptor antagonist, raclopride (0.5 μg/mouse, i.c.v.), did not block the activity. These results indicate that the antinociceptive activity of β-lactotensin is mediated by NT2 and D1 receptors.

Retro-nociceptin methylester, a peptide with analgesic and memory-enhancing activity.

Retro-nociceptin methylester (retro-Noc-ME), which has an oppositely directed structure to that of nociceptin, showed weak affinity for nociceptin receptor and antagonized nociceptin-induced inhibition of contraction in a guinea pig ileum (GPI) assay. The peptide induced analgesia after intracerebroventricular (i.c.v.) administration at a dose of 100 nmol per mouse. Analgesia was not blocked by the opioid antagonist naloxone, which suggests that the analgesia is not mediated by opioid receptor. Furthermore, analgesia caused by retro-Noc-ME was not attenuated after repeated administration, that is, there was an absence of tolerance. The peptide improved learning ability after i.c.v. administration in a step-through experiment in mice.

Anti-analgesic and anti-amnesic effect of complement C3a

In the present study, we found that complement C3a exerted central effects after intracerebroventricular administration in mice. At doses of 3 and 10 pmol/mouse, the peptide showed an antagonistic effect on analgesia induced by morphine and U-50488H, known to be mu- and kappa-opioid receptor agonists, respectively. Moreover, complement C3a improved scopolamine- and ischemia-induced amnesia at a dose of 10 pmol/mouse. Anti-analgesia was not observed by C3a des-Arg at 10 pmol/mouse. The present findings suggest that complement C3a may act as a peptide with anti-opioid activity in the central nervous system.

Designing of an orally active complement C3a agonist peptide with anti-analgesic and anti-amnesic activity.

Complement C3a is an anti-opioid peptide, having anti-analgesic and anti-amnesic effects after intracerebroventricular administration. However, the peptide is inactive after oral administration. Orally active C3a agonist peptide was designed based on the structure of oryzatensin, a C3a agonist peptide derived from rice albumin. Tyr-Pro-Leu-Pro-Arg, a pentapeptide at the carboxyl terminus of oryzatensin is the minimally essential structure for exerting C3a activity. Due to the affinity for mu-opioid receptor, both oryzatensin and Tyr-Pro-Leu-Pro-Arg showed analgesia after intracerebroventricular administration in mice which was blocked by the opioid antagonist naloxone. Tyr-Pro-Leu-Pro-Arg lost opioid activity by substitution the amino terminus tyrosine with other hydrophobic residues. Among the newly designed peptides, Trp-Pro-Leu-Pro-Arg was found to possess the strongest C3a activity. The peptide antagonized morphine-induced analgesia at 300 mg/kg after oral administration and also improved scopolamine- and ischemia-induced amnesia in a step-through passive avoidance test.

Release of hemorphin-5 from human hemoglobin by pancreatic elastase.

Opioid peptide hemorphin-5 (YPWTQ) was released from human hemoglobin by the action of pancreatic elastase. V-hemorphin-5 (VYPWTQ) was also released under the same conditions. The amount of hemorphin-5 was about 1/10 that of V-hemorphin-5. This is the first report showing release of hemorphin-5 only by the action of one enzyme.

Neurite Outgrowth-stimulating Activities of β-Casomorphins in Neuro-2a Mouse Neuroblastoma Cells

Endogenous opioid peptides and opiate drugs are known to affect the development of the nervous system. β-Casomorphins (β-CMs) belong to a family of exogenous opioid peptides derived from the milk protein β-casein by proteolytic fragmentation. We investigated the effects of various fragments and analogues of β-CM on neurite outgrowth in Neuro-2a mouse neuroblastoma cells. The fragments β-CM-5 to -9 and β-CM-5 amide stimulated neurite outgrowth. Fragments shorter than β-CM-5 (β-CM-3, -4, and β-CM-4 amide) and longer than β-CM-9 (β-CM-13 and -21) had no effects. The activity of β-CMs to promote neurite outgrowth does not correlate with their opioid activity in guinea-pig ileum. The effect of the most potent fragment, β-CM-5, was prevented by the μ-opioid receptor-selectiveantagonist D-Phe-Cys2-Tyr3-D-Trp-Orn5-Thr6-Pen7- Thr8-NH2 (CTOP), or by pretreatment with pertussis toxin. These results suggest that the stimulatory effects of β-CMs on neurite outgrowth were mediated through G protein-coupled μ-opioid receptors.