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

The inactivation of the neurohypophyseal hormones arginine vasopressin and oxytocin, both 14C-labelled in the C-terminal glycine residue, by enzymes present in kidney homogenates of various species has been investigated, and some of the enzymes responsible have been partially purified and characterized. The Leu-Gly peptide bond of oxytocin is generally most effectively cleaved by kidney homogenates, although with certain species enzymic activity hydrolyzing the Pro-Leu bond is significant. Degradation of arginine vasopressin is slower than oxytocin in all species studied, and appears to occur by a different overall mechanism since cleavage of the Pro-Arg bond is more significant than hydrolysis of the Arg-Gly bond. The enzyme releasing glycinamide from oxytocin and the "Post-Proline Cleaving Enzyme", which releases C-terminal dipeptide from oxytocin and arginine vasopressin, were partially purified from lamb kidney by ammonium sulfate fractionation and column chromatography. The two enzymes are shown to be separate entities with different pH profiles. The prolyl peptidase activity released the C-terminal dipeptides from oxytocin and arginine vasopressin at similar rates and was inhibited by p-chloromercuriphenylsulfonic acid, 1,10-phenanthroline, L-1-tosylamido-2-phenylethylchloromethyl ketone, Co2+, Ca2+, and Zn2+, but significantly enhanced by dithiothreitol. The prolyl peptidase preparation cleaves proline-containing peptide substrates at the Pro-X bond. The rate of cleavage is dependent on the nature of residue X and with the conditions used there is no cleavage when X equals Pro; however, cleavage occurs when X is a D isomer: [Mpr1, D-Arg8] vasopressin is inactivated at a rate similar to [Mpr1, Arg8]- and [Mpr1, Lys8] vasopressin, suggesting that the known prolonged biological action of [Mpr1, D-Arg8] vasopressin is not due to resistance to the prolyl peptidase. In all characteristics tested the lamb kidney prolyl peptidase was identical to the post-proline cleaving enzyme isolated earlier from human uterus. In vivo experiments in the cat suggested that both the glycinamide-releasing enzyme and post-proline cleaving enzyme are present and effective in inactivating neurohypophyseal hormones in the intact animal.
 ...
PMID:Partial purification and characterization of post-proline cleaving enzyme: enzymatic inactivation of neurohypophyseal hormones by kidney preparations of various species. 0

The endopeptidase, post-proline cleaving enzyme, has been purified 10,500-fold in an overall yield of 18% from lamb kidney. The enzyme possesses a specific activity of 45 mumol/mg/min as tested with the substrate Z-Gly-Pro-Leu-Gly (Km = 6.0 X 10(-5)), has a molecular weight of 115,000, is comprised of two subunits with a molecular weight of 57,000, and exhibits maximal activity at pH 7.5 to 8.0. With the exception of the -Pro-Pro linkage, the -Pro-X-peptide bond (X equals L- and D-amino acid residues) located internally in the peptide sequence can be hydrolyzed (cleavage occurs faster when X = lipophilic side chain as compared to X = acidic side chain). The appropriate -Pro-X- bonds in zinc-free porcine insulin, oxytocin, arginine vasopressin, angiotensin II, bradykinin-potentiating factor were cleaved. Human gastrin, adrenocorticotropic hormone, denatured guinea pig skin collagen, and ascaris cuticle collagen were not degraded. Dipeptides with the structure Z-Pro-LD-X competitively inhibit post-proline cleaving enzyme.
 ...
PMID:Post-proline cleaving enzyme. Purification of this endopeptidase by affinity chromatography. 1 73

This investigation was undertaken to evaluate the functional contribution of the peptide backbone of oxytocin in its interaction with receptor. Corey-Pauling-Koltun models of (Gly-7) deaminooxytocin, deaminotocinamide, and their respective retro-D-analogs built in any specific conformation (e.g., the Walter-Urry model for oxytocin) have a quai-equivalent topochemical arrangement of amino-acid side chains; however, the CO and NH elements of the peptide backbone of the retro-D-analog are reversed. The retro-D-analogs of deaminotocinamide and (Gly-7) deaminooxytocin (prepared using D-alle for L-Ile) and their respective N-formyl derivatives were assayed for uterotonic activity relative to related L-peptides. All retro-D-analogs (tested at concentrations ranging from 10-10 to 10-5 M) were devoid of angonistic (or antagonistic) activity in the isolated rat uterus, except for the retro-D-(D-alle-3, Gly-7) deaminooxytocinamine, which retains a terminal NH-2 group on the tail; the latter is a partial agonist with very low affinity. The results obtained with retro-D-analogs indicate that one or more of the elements of the peptide backbone of the tocinamide ring are essential for "occupation" and "activation" of uterine receptors. Oxytocin action may be the resultant of multiple hydrogen-bonding interactions between CO, NH, NH-2, and OH groups of the hormone with complementary groups on receptor, made possible by appropriate hydrophobic bonding.
 ...
PMID:Contribution of the peptide backbone to the action of oxytocin analogs. 16 58

The oxytocin analogue, 2-nitro-5-azidobenzoylglycyloxytocin (NAB-Gly-oxytocin), has been synthesized and purified. The analogue is a full agonist for the stimulation of osmotic water flow in the toad urinary bladder (one-half maximal activity at 3.2 X 10(-6)M). It also enhances [14C]urea permeability in this tissue. Repetitive photolysis in the presence of NAB-Gly-oxytocin (8 X 10(-6)M) results in a progressive permanent inhibition of oxytocin stimulated urea permeability but does not alter hormone induced 3H2O movement. The inhibition is dependent on the photogeneration of the aryl nitrene intermediate and is relieved by protecting the hormone receptor with excess oxytocin (10(-6)M) during the photolysis. These results suggest that the photodependent permanent inhibition of the response to oxytocin in the toad bladder is due to covalent incorporation of the photoaffinity label, NAB-Gly-oxytocin, into the hormone receptor.
 ...
PMID:Synthesis and characterization of 2-nitro-5-aziodobenzoylglycyloxytocin, an oxytocin photoaffinity label. 20 76

Purified collagenase of Clostridium histolyticum was shown to cleave reduced and S-carboxamidomethylated bovine neurophysin between Cys-13 and Gly-14. The scission resulted in formation of two separable fragments: a smaller peptide arising from residues 1 through 13, and a larger peptide comprising the remainder of the residues of the protein. By dansylation procedures, the smaller peptide was shown to have amino-terminal alanine as expected from the sequence of neurophysin II, and the larger peptide had amino-terminal glycine as anticipated. These results show that collagenase indeed cleaves bovine neurophysin II in accord with the specificity postulated for that enzyme, i.e., scission between -X-Gly- in a sequence of -Pro-X-Gly-Pro-Y-. This result, obtained with a non-collagenous protein substrate, is further confirmation of the specificity of collagenase as established by its action on collagens and on synthetic oligopeptides.
 ...
PMID:Specific cleavage of reduced and S-carboxamidomethylated neurophysin II by the collagenase of Clostridium histolyticum. 20 39

The NH exchange rates in aqueous media of oxytocin and 8-lysine vasopressin (LVP) have been measured by using transfer of solvent saturation method. The data are consistent with a "highly motile" dynamic equilibrium between folded and highly solvated conformations. The highly-motility limit applies to the exchange of NH hydrogens of oxytocin and LVP. Folded structures are more prevalent in oxytocin than in LVP. Partial shielding is indicated for peptide hydrogens of Asn5 and perhaps also Cys6 of oxytocin and for Cys6 of LVP. It is tentatively proposed that the folded conformation of oxytocin in aqueous media may contain a parallel beta-structure in the tocinamide ring consisting of two hydrogen bonds: one between the Tyr2 C = O and Asn5 peptide NH as originally proposed for the preferred conformation of oxytocin in dimethyl sulfoxide (D. W. Urry and R. Walter), and the second between he Cys1 C = O and the Cys6 NH. In LVP the hydrogen bond between the Tyr2 C = O and Asn5 peptide NH appears to be absent. The acylic tripeptide sequences (-Pro-X-Gly-NH2) of both hormones appear to be predominantly solvated. The second-order rate constants for acid catalyzed exchange of the primary amide hydrogens of Gln4, Asn5, and Gly9 of oxytocin are consistently greater for the trans NH than for the corresponding cis NH. This observation can be rationalized in terms of mechanisms involving protonation of either the amide oxygen, or the amide nitrogen, but with limited rotation about the C - N bond.
 ...
PMID:Amide hydrogen exchange rates of peptides in H2O solution by 1H nuclear magnetic resonance transfer of solvent saturation method. Conformations of oxytocin and lysine vasopressin in aqueous solution. 26 22

Deamino-[8-N-methylleucine]oxytocin and deamino-[8-alpha-hydroxyisocaproic acid]oxytocin were synthesized to study the importance of hydrogen bonding between the carboxamide carbonyl of asparagine and the peptide N-H of leucine in stabilizing the biologically active conformation of oxytocin. The analogs were synthesized by coupling deaminotocinoic acid with Pro-Leu(Me)-Gly-NH2 and Pro-HyIc-Gly-NH2, respectively. (HyIc is alpha-hydroxyisocaproic acid). Deamino-[8-N-methylleucine]oxytocin was found to possess 48 +/- 7 units of uterotonic activity, 33 +/- 5 units of avian vasodepressor activity, and 3.15 +/- 1.5 units of antidiuretic activity per mg; deamino-[8-alpha-hydroxyisocaproic acid]oxytocin possessed 134 +/- 12 units of uterotonic activity, 31 +/- 3 units of avian vasodepressor activity, 9.6 +/- 3.0 units of antidiuretic activity, and 0.26 +/- 0.02 unit of pressor activity per mg. Neither of the analogs possesses the peptide N-H at residue 8 required for the formation of a hydrogen bond with the asparagine carboxamide; however, both can assume the conformation needed to evoke the characteristic biological activities of oxytocin although in lower potency. It is concluded that such a hydrogen bond does not constitute a conformational constraint that is essential for hormone action.
 ...
PMID:Biofunctional evaluation of a hydrogen bond linking the ring and tail beta-turns of oxytocin. 29 Oct 4

1. Two enzymes acting on the linear portion of oxytocin: carboxamidopeptidase (releasing Gly . NH2) and prolyl peptidase (releasing Leu-Gly . NH2) were identified in the cytoplasmic fraction of chicken liver. 2. Carboxamidopeptidase was purified 134-fold with a 23% yield, and prolyl peptiase 71-fold with a 20% yield. The specific activity of the final preparations was 181 and 96 microU/mg protein, respectively. 3. The optimum pH for carboxamidopeptidase was 6.0--6.5 and for prolyl peptidase, 7.5. Carboxamidopeptidase activity was inhibited by Mn2+, Zn2+, Ca2+, Co2+, and stimulated by EDTA; the activity of prolyl peptidase was inhibited by Zn2+ and Mn2+. The Km value of both enzymes for oxytocin was 1.5--2.4 microM.
 ...
PMID:Partial purification and characterization of the oxytocin-inactivating enzymes from chicken liver. 39 2

Oxytocin (OT) was synthesized employing the solid phase method. Resins made of copolymers of polystyrene-1%-crosslinked with divinylbenzene gave better yields (73-95%) of Z-Cys(Bzl)-Tyr(Bzl)-Ile-Gln-Asn-Cys(Bzl)-Pro-Leu-Gly-NH2 (I) than 2%-crosslinked resins (10--56%). Reduction of I with Na-liq.NH3 and oxidation with I2-MeOH at -40 degrees minimized dimer and polymer formation, and resulted in good yields (49--54%) of OT. The large volumes of MeOH required when several grams of I are reduced and then oxidized were rapidly evaporated in vacuo, and the residue was desalted by dissolving the peptide in a small volume of glacial acetic acid and filtering to remove the salt. OT was purified by adsorption chromatography on a silica gel column with combinations of MeOH-CHCl3 of graded polarity. Oxytocin elutes with 33% MeOH-CHCl3. After two purification steps by adsorption chromatography, the resulting OT was found to be homogeneous. The hormone was characterized chemically and found to be active biologically.
 ...
PMID:Synthesis of oxytocin using iodine for oxidative cyclization and silica gel adsorption chromatography for purification. 42 90

Cyclo(Leu-Gly), the enzymatically resistant diketopiperazine formally derived from the C-terminal dipeptide sequence of oxytocin, exhibits activity in several behavioral systems. The distribution of cyclo(Leu-14C(U)Gly) in brain, and the time course of the disappearance of this labeled peptide from brain and plasma after subcutaneous injection into mice have been studied. The intact peptide was distributed equally in the five cerebral areas studied, for up to 96 hours after injection. Two exponential components were determined for peptide disappearance rates in plasma and brain; peptide half-lives in plasma up to 10 hr and from 24--96 hr after injection were, respectively, 0.8 and 33 hr; in brain, 1.0 and 42 hr. The peptide was found to accumulate in brain intracellular space to some degree. The time course of distribution of labeled cyclo(Leu-Gly) in subcellular fractions of mouse brain was also examined, and the concentration of peptide in the synaptosomal fraction was significantly correlated with the degree of protection against puromycin-induced amnesia of a maze-learning test. The results obtained not only confirm that cyclo(Leu-Gly) penetrates brain tissue intact and remains intact after peripheral administration in order to exert its behavioral effects, but, moreover, suggest an intriguing dynamic relationship between peptide concentration in the synaptosomal fraction and behavioral activity.
 ...
PMID:Distribution, survival and biological effects in mice of a behaviorally active, enzymatically stable peptide: pharmacokinetics of cyclo(Leu-Gly) and puromycin-induced amnesia. 57 1


1 2 3 4 5 6 7 8 9 10 Next >>