Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interrelationship of several physiological receptors which influence the hydroosmotic response of the toad urinary bladder was studied employing neurohypophyseal peptides, prostaglandin E(1), theophylline, and cyclic nucleotides. The binding property of agonists (pD(2)), synergists (pS(2)), competitive antagonists (pA(2)), and noncompetitive antagonists (pD(2)') was determined after a suitable methodology had been developed. A series of neurohypophyseal peptides was examined in detail for their catalytic activity. It was found that the replacement of the hydroxy radical of the tyrosine residue in oxytocin by a methoxy and then by an ethoxy radical led to a progressive decline in the catalytic activity of the hormone-corresponding to a change from agonist to partial agonist to competitive antagonist. [4-Leucine]-mesotocin behaved as a competitive antagonist of oxytocin. Prostaglandin E(1) (PGE(1)) was found to be a noncompetitive inhibitor of neurohypophyseal peptides and theophylline; whereas the maximal hydroosmotic response of the bladder to [2-O-methyltyrosine]-oxytocin and theophylline was greatly depressed by PGE(1), the response to saturating concentrations of oxytocin was only slightly diminished-a finding which reveals a "receptor reserve" for oxytocin. Saturating concentrations of [2-O-ethyltyrosine]-oxytocin, inactive per se, potentiate theophylline-disclosing a "threshold phenomenon" for the mediation of neurohypophyseal hormone action. It is concluded that neurohypophyseal peptides are capable of producing graded effects on adenyl cyclase both below and above the range of enzyme activity which evokes graded changes in membrane permeability.
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PMID:Threshold and receptor reserve in the action of neurohypophyseal peptides. A study of synergists and antagonists of the hydroosmotic response of the toad urinary bladder. 543 69

Studies were carried out on the right auricle of the right atrium of two-day-old rats placed in a special chamber perfused with Ringer-Locke solution at room temperature. The contractions rate of the auricle was counted with the use of a stereomicroscope. The following amino acids dissolved in Ringer-Locke solution were tested: glycine, glutamic acid, serine, alanine, aspartic acid, gamma aminobutyric acid, leucine, and peptides: vasopressin and oxytocin. Glutamic acid in a concentration of 10(-1) mol/l induced a decrease in auricle contraction rate by 25%. Alanine in concentration 10(-2) mol/l induced a decrease by 22%. Leucine in concentration 10(-2) mol/l induced a decrease by 16% and in concentration ten times higher a decrease by 28%. The other tested amino acids, vasopressin and oxytocin in concentration used had no influence on the rate of contraction frequency of the isolated auricle.
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PMID:The influence of amino acids, vasopressin and oxytocin on spontaneous contraction of the right auricle of the right atrium of two-day-old rats in vitro. 654 86

Leucine aminopeptidases (LAPs) are metallopeptidases that cleave N-terminal residues from proteins and peptides. While hydrolyzing Leu substrates, LAPs often have a broader specificity. LAPs are members of the M1 or M17 peptidase families, and therefore the LAP nomenclature is complex. LAPs are often viewed as cell maintenance enzymes with critical roles in turnover of peptides. In mammals, the M17 and M1 enzymes with LAP activity contribute to processing peptides for MHC I antigen presentation, processing of bioactive peptides (oxytocin, vasopressin, enkephalins), and vesicle trafficking to the plasma membrane. In microbes, the M17 LAPs have a role in proteolysis and have also acquired the ability to bind DNA. This property enables LAPs to serve as transcriptional repressors to control pyrimidine, alginate and cholera toxin biosynthesis, as well as mediate site-specific recombination events in plasmids and phages. In plants the roles of the M17 LAPs and the peptidases related to M1 LAPs are being elucidated. Roles in defense, membrane transport of auxin receptors, and meiosis have been implicated.
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PMID:Leucine aminopeptidases: diversity in structure and function. 1713 98