Sensory peptide

The Protein and Bioactive Peptide Sequences (BIOPEP) is a public database (Dziuba et al., 1999) containing 707 proteins, 2123 bioactive peptides, 65 allergenic proteins with their epitopes, and 224 sensory peptides and amino acids. Databases include information such as sequence, number of amino acid residues, molecular weight, activity, and references. BIOPEP can be browsed online and the user can search for a specific sequence. 

Normally substance P is increased in chemical bums [19], playing an important role in immune response, inflammation, pain and wound healing, promoting the regeneration of sensory peptide nerve fibers in the skin that underwent chanical... 

In general, nonconventional protein foods must be competitive with conventional plant and animal protein sources on the bases of cost delivered to the consumer, nutritional value to humans or animals, functional value in foods, sensory quality, and social and cultural acceptability. Also, requirements of regulatory agencies in different countries for freedom from toxins or toxic residues in single-cell protein products, toxic glycosides in leaf protein products, pathogenic microorganisms, heavy metals and toxins in fish protein concentrates, or inhibitory or toxic peptide components in synthetic peptides must be met before new nonconventional food or feed protein products can be marketed. 

CGRP has a wide distribution in the nervous system (19) and was the first peptide to be localized to motoneurons (124). It is also found in primary sensory neurons where it is colocalized with substance P (125). CGRP is derived from a precursor stmcturaHy related to the calcitonin precursor. The latter precursor produces two products, calcitonin itself and katacalcin, while the CGRP precursor produces one copy of CGRP (123). Like other peptides, CGRP is cleaved from its precursor by tryptic breakdown between double basic amino acid residues. 

Capsaicin, an active ingredient in red pepper, is well known for its ability to release and deplete substance P in sensory C fibers. However, this action is not specific for substance P, as neurokinin A, calcitonin gene-related peptide (CGRP), and somatostatin also are released. 

Nociceptin and orphanin are synonyms for the peptide that acts at an opioid-like receptor. Nociceptin may act by inhibiting tachykinin release from sensory C-fibres, and a clinical trial has started to test its effects on cough. 

The surrounding redness caused by the vasodilatation of local blood vessels in the skin (hyperaemia). Histamine released at the site of contact acts on sensory nerve endings in the skin. Impluses travel along the axon to other peripheral branches of the same neuron to cause release of vasodilataory peptide neurotransmitters from nerve endings serving a wider area of skin than the initial contact point. Impluses reaching the CNS are interpreted as itch and pain. 

Hi-receptors in the adrenal medulla stimulates the release of the two catecholamines noradrenaline and adrenaline as well as enkephalins. In the heart, histamine produces negative inotropic effects via Hr receptor stimulation, but these are normally masked by the positive effects of H2-receptor stimulation on heart rate and force of contraction. Histamine Hi-receptors are widely distributed in human brain and highest densities are found in neocortex, hippocampus, nucleus accumbens, thalamus and posterior hypothalamus where they predominantly excite neuronal activity. Histamine Hrreceptor stimulation can also activate peripheral sensory nerve endings leading to itching and a surrounding vasodilatation ( flare ) due to an axonal reflex and the consequent release of peptide neurotransmitters from collateral nerve endings. 

ATP with calcitonin gene-related peptide and substance P in sensory-motor nerves... 

The excitatory amino acids are found in most sensory fibres of both large- and small-diameter fibres and, in the latter, they are co-localised with peptides such as substance P. The co-existence of these two transmitters suggests that they are released together in... 

The release of some peptides may differ from that of other transmitters, depending on the firing rate of the neurons. The large vesicles needed to store a peptide may need a greater rate of depolarisation for membrane fusion and release of the contents. In the salivary gland the release of vasoactive intestinal polypeptide requires high-frequency stimulation whereas acetylcholine is released by all stimuli. Due to the complexities and problems of access to CNS synapses it is not known if the same occurs here but there is no reason why this should not. In sensory C-fibres a prolonged stimulus appears to be a prerequisite for the release of substance P. 

Nerve receptors, or nociceptors, may release substance P, a peptide that causes vasodilation when released.20 This dilation occurs mainly through substance P-induced production of the vasodilator nitric oxide. Substance P also generates the release of histamine, leading to bradykinin release and activation of an inflammatory process. Capsaicin relieves pain by stimulating the release of substance P from sensory nerve fibers, which ultimately depletes stores of substance P. 

Membrane-associated receptors are linked to transducing proteins (like G-proteins) in the inner portion of the membrane. G-protein coupled receptor (GPCR) families comprise a major class of the receptors that are pharmacologically relevant, such as muscarinic acetyl choline receptors, adrenoceptors, dopamine receptors, serotonine, opiate, peptide hormone, purinerg receptors, and also sensory chemoreceptors. A large variety of subtypes are described in the pharmacological literature. 

---