RESUMEN
There are many examples of biologically active food proteins, with physiological significance beyond the pure nutritional requirements that concern available nitrogen for normal growth and maintenance. Moreover, there are many physiologically active peptides, derived by protease activity from various food protein sources; however, relationships between structural properties and functional activities have not been completely elucidated. Many bioactive peptides have in common structural properties that include a relatively short peptide residue length (e.g. 2-9 amino acids), possessing hydrophobic amino acid residues in addition to proline, lysine or arginine groups. Bioactive peptides are also resistant to the action of digestion peptidases. Antihypertensive peptides, known as Angiotensin I converting enzyme (ACE) inhibitors have been derived from milk, corn and fish protein sources. Peptides with opioid activities are derived from wheat gluten or casein, following digestion with pepsin. Exorphins, or opioid peptides derived from food proteins such as wheat and milk (e.g. exogenous sources) have similar structure to endogenous opioid peptides, with a tyrosine residue located at the amino terminal or bioactive site. Immunomodulatory peptides derived from tryptic hydrolysates of rice and soybean proteins act to stimulate superoxide anions (reactive oxygen species-ROS), which triggers non-specific immune defense systems. Antioxidant properties that prevent peroxidation of essential fatty acids have also been shown for peptides derived from milk proteins. The addition of a Leu or Pro residue to the N-terminus of a His-His, dipeptide will enhance antioxidant activity and facilitate further synergy with non-peptide antioxidants (e.g. BHT). We also show herein, that the tryptic digests of casein yielding caseinophosphopeptides exhibits both hydrophilic and lipophilic antioxidant activity due to both metal ion sequestering and quenching of ROS. The separation and purification of bioactive peptides which will involve development of automated and continuous systems is an important field for Food chemists. Much effort has been given to develop selective column chromatography methods that can replace batch methods of salting out, or using solvent extraction to isolate and purify bioactive peptides. Advances here will enable recovery of bioactive peptides with minimal destruction thus enabling utilization by returning these active peptides to functional food or specific nutraceutical applications.
Asunto(s)
Proteínas en la Dieta/aislamiento & purificación , Alimentos , Péptidos/química , Péptidos/aislamiento & purificación , Adyuvantes Inmunológicos/química , Adyuvantes Inmunológicos/aislamiento & purificación , Adyuvantes Inmunológicos/farmacología , Antiinfecciosos/química , Antiinfecciosos/aislamiento & purificación , Antiinfecciosos/farmacología , Antioxidantes/química , Antioxidantes/aislamiento & purificación , Antioxidantes/farmacología , Productos Lácteos , Grano Comestible/química , Proteínas del Huevo/química , Proteínas del Huevo/aislamiento & purificación , Productos Pesqueros , Humanos , Minerales/metabolismo , Péptidos Opioides/química , Péptidos Opioides/aislamiento & purificación , Péptidos Opioides/farmacología , Proteínas de Plantas/química , Proteínas de Plantas/aislamiento & purificaciónRESUMEN
In order to investigate the processing of OFQ containing peptides in the hypothalamus we have developed a sensitive and quantitative radioimmunoassay for OFQ. We fractionated rodent and monkey hypothalamic extracts by reversed-phase high performance liquid chromatography and found that the extracts contained multiple peaks of OFQ immunoreactivity with the major peak co-eluting with synthetic OFQ1-17. Mouse hypothalamic extracts were also fractionated by SDS-PAGE to determine the apparent molecular weights of molecules containing the OFQ peptide. Multiple peaks of OFQ immunoreactivity, ranging in size from approximately 1 to 30 kilodaltons, were detected by this method. These results suggest that OFQ1-17 is processed to smaller peptides in mouse and monkey hypothalamic neurons.
Asunto(s)
Hipotálamo/química , Péptidos Opioides/análisis , Secuencia de Aminoácidos , Animales , Cromatografía Líquida de Alta Presión , Electroforesis en Gel de Poliacrilamida , Femenino , Hipotálamo/citología , Hipotálamo/metabolismo , Hibridación in Situ , Macaca mulatta , Masculino , Ratones , Datos de Secuencia Molecular , Peso Molecular , Péptidos Opioides/aislamiento & purificación , Péptidos Opioides/metabolismo , Fragmentos de Péptidos/análisis , Fragmentos de Péptidos/aislamiento & purificación , ARN Mensajero/análisis , Radioinmunoensayo , Ratas , Ratas Wistar , NociceptinaRESUMEN
A heptadecapeptide was identified and purified from porcine brain tissue as a ligand for an orphan heterotrimeric GTP-binding protein (G protein)-coupled receptor (LC132) that is similar in sequence to opioid receptors. This peptide, orphanin FQ, has a primary structure reminiscent of that of opioid peptides. Nanomolar concentrations of orphanin FQ inhibited forskolin-stimulated adenylyl cyclase activity in cells transfected with LC132. This inhibitory activity was not affected by the addition of opioid ligands, nor did the peptide activate opioid receptors. Orphanin FQ bound to its receptor in a saturable manner and with high affinity. When injected intracerebroventricularly into mice, orphanin FQ caused a decrease in locomotor activity but did not induce analgesia in the hot-plate test. However, the peptide produced hyperalgesia in the tail-flick assay. Thus, orphanin FQ may act as a transmitter in the brain by modulating nociceptive and locomotor behavior.
Asunto(s)
Proteínas de Unión al GTP/metabolismo , Péptidos Opioides/aislamiento & purificación , Péptidos Opioides/metabolismo , Receptores de Neuropéptido/metabolismo , Receptores Opioides/metabolismo , Inhibidores de Adenilato Ciclasa , Secuencia de Aminoácidos , Analgésicos/farmacología , Animales , Células CHO , Colforsina/farmacología , Cricetinae , Hipotálamo/química , Inyecciones Intraventriculares , Inyecciones Espinales , Ligandos , Ratones , Datos de Secuencia Molecular , Actividad Motora/efectos de los fármacos , Péptidos Opioides/química , Péptidos Opioides/farmacología , Dimensión del Dolor , Porcinos , Transfección , NociceptinaRESUMEN
Macrophages have a prominent role in the injury response of the brain, yet the molecular mechanisms that control their invasion to the site of neuronal degeneration is unknown. After removal of the posterior cortex at birth, there is massive and specific targeting of nonresident macrophages to axotomized neurons in the lateral thalamus. The present study has identified an injury-induced, brain-derived chemotactic factor (BDCF) capable of eliciting chemotactic responses from resident peritoneal macrophages and brain macrophages. Conditioned media collected from tissue slices containing the axotomized central nervous system neurons exhibit BDCF activity. Initial experiments indicated that BDCF is a small peptide and, thus, we used specific pharmacologic reagents to characterize further BDCF activity. Naloxone, a pan opioid receptor antagonist, completely blocks BDCF activity. Although both kappa and mu opioid receptor antagonists failed to modify BDCF-induced macrophage chemotaxis, two specific delta receptor antagonists blocked BDCF. Analysis of BDCF by reverse phase HPLC and RIA revealed peak chemotactic activity in fractions consistent with the presence of an opioid peptide. The results suggest that cells in the brain respond to neuronal injury by producing and releasing opioids that can initiate a specific macrophage response.