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 interchange reaction of disulfides was caused by the copper(II)/ascorbic acid/O2 system. The incubation of two symmetric disulfides, L-cystinyl-bis-L-phenylalanine (PP) and L-cystinyl-bis-L-tyrosine (TT), with L-ascorbic acid and CuSO4 in potassium phosphate buffer (pH 7.2, 50 mM) resulted in the formation of an asymmetric disulfide, L-cystinyl-L-phenylalanine-L-tyrosine (PT), and the final ratio of PP:PT:TT was 1:2:1. As the reaction was inhibited by catalase and DMSO only at the initial time, hydroxyl radical generated by the copper(II)/ascorbic acid/O2 system seemed to be responsible for the initiation of the reaction. Oxytocin and insulin were denatured by this system, and catalase and DMSO similarly inhibited these denaturations. As the composition of amino acids was unchanged after the reaction, hydroxyl radical was thought to cause the cleavage and/or interchange reaction of disulfides to denature the peptides.
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PMID:Interchange reaction of disulfides and denaturation of oxytocin by copper(II)/ascorbic acid/O2 system. 359 55

Changes in the mineral composition of mare milk during lactation were studied. Milk samples were obtained from five Thoroughbred mares one to three times weekly from the first to the eighth week of lactation and from two of the mares for an additional 8 wk. Samples averaging 500 mL were obtained after oxytocin was administered to the mares. Each sample was analyzed for total solids, ash, calcium, phosphorus, magnesium, sodium, potassium, copper and zinc. The concentration of all constituents except sodium and potassium decreased throughout lactation. The rates of decline of ash, calcium, phosphorus and magnesium concentration were similar, but the rates of decline of the other elements differed. Thus, the mineral composition of mare milk should be described in terms of the stage of lactation of the mare. The total solids and ash content of mare milk were 12 and 0.61% respectively, at the end of the first week of lactation, 10.5 and 0.45% at 4 wk, 10 and 0.38% at 8 wk and 10.2 and 0.32% at 16 wk. The calcium, phosphorus and magnesium concentrations at the end of the same periods were 1345, 943 and 118 micrograms/g of milk at 1 wk; 1070, 659 and 86 at 4 wk; 831, 574 and 58 at 8 wk and 700, 540 and 43 micrograms/g of milk at 16 wk. Copper and zinc concentrations were 0.85 and 3.1, 0.55 and 2.2, 0.29 and 1.9 and 0.28 and 1.8 microgram/g of milk at 1, 4, 8 and 16 wk, respectively.
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PMID:Lactation in the horse: the mineral composition of mare milk. 379 22

An identical cytochrome b561 was found to be an integral component of both chromaffin vesicles from adrenal medulla and neurosecretory vesicles from posterior pituitary by spectrophotometric and immunological techniques. The neurosecretory vesicles had 6.8 micrograms of cytochrome/mg of membrane protein versus 69 micrograms/mg in chromaffin vesicles. This cytochrome was also immunologically detected in various regions of bovine brain and was immunologically distinct from the cytochrome found in serotonin-containing vesicles from platelets. Dopamine beta-hydroxylase involved in the biosynthesis of catecholamines was not present in neurosecretory vesicles, suggesting an alternative functional role for the cytochrome in these vesicles. Neurosecretory vesicles do contain a mixed function oxidase (peptidyl alpha-amidase) which appears to be involved in alpha-amidation of the carboxyl termini of vasopressin and oxytocin. We suggest that cytochrome b561 in the two vesicles may be functionally associated with different ascorbic acid-dependent, copper-containing mixed function oxidases: dopamine beta-hydroxylase and peptidyl alpha-amidase.
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PMID:An identical cytochrome b561 is present in bovine adrenal chromaffin vesicles and posterior pituitary neurosecretory vesicles. 671 27

A post-proline cleaving enzyme [post-proline endopeptidase: EC 3.4.21.26] was purified from lamb brain by a series of column chromatographies on DEAE-Sephadex, hydroxyapatite and Sephadex G-150. The purified enzyme appeared homogeneous on disc gel and sodium dodecyl sulfate (SDS) gel electrophoreses. The enzyme was most active at pH 7.0 with carbobenzoxy-Gly-Pro-beta-naphthylamide (Z-Gly-Pro-2-NNap) as a substrate and catalyzed the hydrolysis of oxytocin, vasopressin, thyrotropin releasing hormone (TRH), substance P, luteinizing hormone releasing hormone (LH-RH), and angiotensin at the carboxyl side of their proline residues, except for the Pro2-Lys3 bond in substance P. From the results of subsite mapping using synthetic peptides, five subsites, S3 to S2', for substrate interaction with the enzyme were deduced to be present, and high stereospecificity was observed at S2, S1, and S1'. The isoelectric point of the enzyme was at pH 4.9, and the molecular weights estimated by gel filtration and SDS gel electrophoresis were 74,000 and 77,000, respectively. The enzyme was markedly inhibited by diisopropylphosphoro fluoridate (DFP), carbobenzoxy-Gly-Pro-chloromethyl ketone (Z-Gly-Pro-CH2Cl), p-chloromercuribenzoate (PCMB), Hg2+, and Cu2+ ions. These enzymatic and protein chemical properties of post-proline cleaving enzyme from lamb brain closely resemble those of the lamb kidney enzyme, except for the molecular weight. In the present work, however, we decided that the molecular weight of the enzyme from lamb kidney was also 74,000, which is different from that reported previously (J. Biol. Chem. 251, 7593 (1976) but is in accord with the value of post-proline cleaving enzyme from lamb brain.
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PMID:Post-proline cleaving enzyme from lamb brain. 702 30

Copper(II) complexes of oxytocin, 4-Glu-oxytocin, 5-Asp-oxytocin, and GlyGlyGly-Lys8-vasopressin were studied by potentiometric, EPR, and UV-visible spectroscopic methods. The formation of 4N-coordinated complexes was characteristic of all ligands. This type of coordination is especially favored for oxytocin due to the specific conformation of the ring coupled by the disulfide bridge. The coordination of the gamma-carboxylate group of 4-Glu-oxytocin and a disulfide sulfur atom of GlyGlyGly-Lys8-vasopressin was reported to occur in the 2N-complexes over medium pH range.
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PMID:Potentiometric and spectroscopic studies on the copper(II) complexes of peptide hormones containing disulfide bridges. 759 72

Oxytocin (OT; Cys-Tyr-Ile-Gln-Asn-Cys-Pro-leu-Gly), a posterior pituitary peptide hormone, is characterized by a Cys1-Cys6 disulfide bond in its stable, isolated state. This paper describes a simple, one-step method for the production of OT in its reduced, dithiol form (OT dithiol), free of reducing agent. The effects of temperature, pH, and metal-ion chelators on the autoxidation of OT dithiol were examined to establish if this form is likely to persist under biological conditions. It was found that OT dithiol has a half-life of 1.8h with respect to reformation of OT disulfide at 37 degrees C and pH 6.9 in the presence of the copper chelators, DTPA and neocuproine. S-Nitrosation of OT dithiol by acidified nitrite at pH 3.0 was examined by absorption spectroscopy and HPLC-UV-MS, which revealed that both singly and doubly S-nitrosated OT are formed. These results suggest novel chemical aspects to OT signaling, the biological implications of which are discussed here.
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PMID:Reduction and S-nitrosation of the neuropeptide oxytocin: implications for its biological function. 1769 43

The structures of a [Ni(II), Cu(II)- - -oxytocin] complex were investigated by electrospray ionization-mass spectrometry in positive mode. The fragmentation patterns of the [Ni(II), Cu(II) + OT](2+) complex were analyzed by tandem mass spectrometry and multiple mass spectrometry in the gas-phase. Conformations of metalII ion binding to oxytocin (OT) have been studied to explain the biological activity difference in the physiological solution. The [Ni(II) + OT](2+) and [Cu(II) + OT](2+) complexes were observed as the main ions in MS spectra. The Cys1-Tyr2-Ile3-Gln4 sequence of oxytocin is suggested to be a binding site for the [Ni(II) + OT](2+) gas-phase complex and Ile3-Gln4-Asn5-Cys6 sequence for the [Cu(II) + OT](2+) gas-phase complex. The specific binding site of CuII ion in the [Cu(II) + OT](2+) complex is explained as a reason of the negligible effect on the [Cu(II)- - -oxytocin] biological activity in aqueous solution.
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PMID:Determination of a binding site of Cu and Ni metal ions with oxytocin peptide by electrospray tandem mass spectrometry and multiple mass spectrometry. 1917 95

The study was conducted to examine effects of a selective copper(I) chelator, neocuproine on the spontaneous or oxytocin-induced contractions in isolated ovariectomized non-pregnant rat, pregnant rat and pregnant human uterus. Uterus activity was evaluated in tissues obtained from bilaterally ovariectomized non-pregnant rats on the 21st day of the operation (n = 24), pregnant rats on the 19-21st day of gestation (n = 24) and women undergoing caesarean section at 38-42 weeks of pregnancy (n = 15). Neocuproine (100 microM) significantly suppressed the amplitude and frequency of the spontaneous contractions in the ovariectomized non-pregnant rat uterus while this agent facilitated the frequency of the spontaneous or oxytocin-induced contractions in the pregnant rat and human uterus without altering the amplitude of these contractions. At high concentration of 200 microM, neocuproine could enhance the amplitude of the contractions in the pregnant uterus. These effects were blocked by a purinergic receptor antagonist, suramin (100 microM) and did not occur following the administration of neocuproine-copper(I) complex or copper(II) chelator cuprizone. alpha, beta-methylene ATP increased the amplitude and frequency of contractions in the pregnant uterus, but not affected the contractions in the ovariectomized non-pregnant rat uterus, and neocuproine potentiated this facilitation effect. However, the suppressive effect of neocuproine on the ovariectomized non-pregnant rat uterus increased in the presence of alpha,beta-methylene ATP. Beta-adrenoceptor blocker, propranolol or nitric oxide synthase inhibitor, L-nitroarginine did not affect the responses to neocuproine. These findings suggest that neocuproine can affect the uterus contractile activity by modulation purinergic excitatory responses and that copper(I)-sensitive mechanisms may play a role in this effect.
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PMID:Differential effect of neocuproine, a copper(I) chelator, on contractile activity in isolated ovariectomized non-pregnant rat, pregnant rat and pregnant human uterus. 1924 49

Trapped oxytocin (OT) peptide dianions and copper-oxytocin complex dianions are subjected to electron detachment when irradiated by a UV light. Electron photodetachment experiments as a function of the laser wavelength were performed on the native disulfide-containing ring oxytocin, the reduced dithiol oxytocin, and the Cu(II)-oxytocin complex. The electron detachment yield was used to monitor the excited electronic spectrum of the trapped ions. The spectra can be used as a fingerprint of the ionization state of the tyrosine chromophore under different structural environments. In gas-phase oxytocin dianion [OT-2H](2-), the tyrosine is deprotonated while it is neutral for the reduced form of oxytocin [OT(SH)-2H](2-). Optical spectra for the copper complex dianion [OT-4H+Cu](2-) are in favor of a neutral tyrosine in the complex. A structure with the metal cation chelated to four deprotonated amide groups is proposed for this complex.
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PMID:Optical properties of isolated hormone oxytocin dianions: ionization, reduction, and copper complexation effects. 1945 66

We present a joint experimental and theoretical investigation of the structural and optical properties of copper-oxytocin dications in the gas phase. Ion mobility and UV photodissociation experiments were performed, allowing the investigation of the influence of the Cu(2+) ion on the structural and optical properties of oxytocin. Density functional theory calculations were performed to find low energy structures for the bare and complexed peptide and to characterize optical spectral features. Copper complexation induces a drastic change in the structure of the oxytocin peptide. In particular, we predict a 4N chelation of the copper cation which leads to a contraction of the oxytocin ring. The gas phase lowest-energy structures are compared with the X-ray crystal structure of the oxytocin molecule bound to its receptor protein. The optical spectrum of oxytocin complexed with the copper cation displays a global enhancement of the photofragmentation yield as compared to the one recorded for the doubly protonated oxytocin. Moreover, experimental and calculated optical spectra of protonated tyrosine have also been determined, since its leading features are present in oxytocin as well.
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PMID:Optical and structural properties of copper-oxytocin dications in the gas phase. 1962 11


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