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)

An enzyme which catalyzes the deamidation of thyroliberin (TRF; less than Glu-His-Pro-NH2) has been purified 110-fold from extracts of bovine anterior pituitary by ammonium sulfate fractionation, ion exchange chromatography on DEAE-cellulose, and gel filtration. This enzyme of 76,000 molecular weight (as estimated by gel filtration) exhibits maximal activity at neutral pH (optimum pH 7.4 to 7.6) in buffers of high ionic strength supplemented with thiol-protecting agents. As indicated by the strong inhibition of the enzymatic activity by N-ethylmaleimide and Hg2+, as well as by the extreme sensitivity toward diisopropyl fluorophosphate, -SH, and -OH residues apparently represent essential functional groups of the enzyme. The stereospecific deamidation of TRF (Km = 4.1 . 10(-4) M) is inhibited competitively by TRF analogues which contain proline or by the proline containing biologically active peptides luliberin (LH-RF), oxytocin, vasopressin, angiotensin II, and Substance P. TRF analogues without proline or peptide amides without proline are ineffective. This enzyme cleaves the appropriate Pro-X bonds in luliberin, angiotensin II, pyroGlu-His-Pro-Gly-NH2, and the collagenase substrate Z-Gly-Pro-Leu-Gly-Pro. Thus, it may be characterized as a post-proline-cleaving enzyme.
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PMID:Characterization of "thyroliberin-deamidating enzyme" as a post-proline-cleaving enzyme. Partial purification and enzyme-chemical analysis of the enzyme from anterior pituitary tissue. 11 64

The rate of hydrolysis of several aminoacyl-4-nitroanilides by rat hypothalamic arylamidases was investigated. The activity of these enzymes which were mainly found in the 105 000 times g supernatant fraction of homogenates of the hypothalamus and other parts of the brain was shown to depend upon the presence of metal ions and free thiol groups, and to be inhibited by puromycin. As previous investigations had shown that Cys-NA is an appropiate substrate for measuring hormone effects on hypothalamic arylamidases, L-cystine arylamidase and its interaction with various peptide hormones were examined in detail. It could conclusively be shown that this enzyme interacts particularly with oligopeptides. Its activity was competitively inhibited by TRF, oxytocin, lysine vasopressin, and LH-RH. It was also shown that the biological activity of LH-RH and its inhibitory effect on the hydrolysis of L-cystine-bis-p-nitroanilide decreased when it was incubated for various periods of time with the 105 000 times g supernatant of rat hypothalumus homogenate.
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PMID:Inactivation of luteinizing hormone releasing hormone by rat hypothalamic L-cystine arylamidase. 80 61

To clarify whether various neuropeptides found in the hypothalamus act directly on a pituitary adenoma causing Nelson's syndrome, we examined the influence of these peptides on the secretion of immunoreactive ACTH, beta-endorphin, and melanotropins, the proopiomelanocortin (POMC)-derived peptides, by the cultured pituitary adenoma from a patient with Nelson's syndrome. Results showed that somatostatin-14 and somatostatin-28 suppressed the secretion of POMC-derived peptides by the adenoma and that somatostatin-28 was as potent as somatostatin-14. Other neuropeptides such as arginine vasopressin, vasoactive intestinal polypeptide, and oxytocin stimulate the secretion of POMC-derived peptides. Substance P, TRF, Met-enkephalin and Leu-enkephalin were also found to modulate the secretion of POMC-derived peptides. This suggests that the adenoma may have multiple receptors to various neuropeptides.
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PMID:Effects of various neuropeptides on the secretion of proopiomelanocortin-derived peptides by a cultured pituitary adenoma causing Nelson's syndrome. 612 87

Recent work in our laboratory on the role of peptides to influence release of pituitary hormones by direct action on the gland and also some of the interactions of these peptides at the hypothalamic level to alter release of pituitary hormones will be reviewed. Considerable evidence from hypothalamic stimulation and lesion studies suggests the existence of a separate FSH-releasing factor (FSHRF). We have been able to purify a bioactive FSHRF which appears to be distinct from LHRH. Consequently, we believe that a distinct FSHRF will ultimately be isolated. With regard to prolactin, it is now clear that it is under dual control by both prolactin-inhibiting (PI) and prolactin-releasing factors (PRF). Although dopamine acts as a PIF, our recent fractionation studies indicate the existence of a peptidic PIF in hypothalamic extracts which can be separated from dopamine and GABA. The peptidic PIF is eluted from Sephadex in the same position originally described by us a number of years ago. Thus, inhibitory control is probably mediated by a combination of factors which would include dopamine, possibly GABA and a peptidic PIF. A number of peptides have been shown to have PRF activity which include TRF and also VIP. In recent studies, we have shown a prolactin-releasing action of oxytocin on male hemipituitaries or dispersed pituitary cells. Furthermore, high doses of oxytocin given intravenously released prolactin in male rats. There is a correlation between estrogen-induced prolactin release and an increase in plasma oxytocin and a correlation between suckling-induced oxytocin and prolactin release. These results suggest that oxytocin may be an important PRF.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Recent studies on the role of brain peptides in control of anterior pituitary hormone secretion. 614 38

The present investigation was conducted in order to get more insight into the mechanism of action of vasopressin (VP) on ACTH secretion and characterize VP interaction with putative receptor sites at the level of the anterior pituitary gland. The experimental procedure consisted of increasing ACTH release from incubated pituitary fragments as induced by VP in the presence or absence of oxytocin (OT) and various releasing factors. Our results show that, whereas OT was able to depress VP-induced release of ACTH (Fig. 2), TRF (Fig. 3), LH-RH (Fig. 4) and crude "CRF" extract (Fig. 1) it did not exhibit any significant inhibitory effect. This provides indirect evidence for the presence of specific pituitary sites for VP and related peptides such as OT. The latter, however, was devoided of corticotrophic releasing properties.
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PMID:[Specificity of the effect of vasopressin at the anterior pituitary level (author's transl)]. 625 Dec 9