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 enzyme kinetic parameters of the degradation of luteinizing hormone-releasing hormone (LH-RH) and L-cystine-bis-(4-nitroanilide) (Cys-NA) by rat hypothalamic (HYP) and pituitary (PIT) extracts and the effect of various oligopeptides on the rate of LH-RH inactivation were investigated in vitro. The 105,000 x g supernatant of 1 rat HYP inactivated 57 microgram LH-RH during a 30 min incubation (Km = 12.4 microM, V max = 2.33 microgram LH-RH/mg protein/min), and of one rat anterior PIT, 48 microgram LH-RH during 30 min of incubation (Km = 12.2 microM, V max = 8.0 microgram LH-RH/mg protein/min). The synthetic substrate Cys-NA competitively inhibited LH-RH degradation with a Ki of 8.5 microM in the HYP and 6 microM in the PIT enzyme preparation. Vice versa, LH-RH also competitively inhibited the cleavage of Cys-NA with inhibition constants of 14 microM (HYP) and 15 microM (PIT) indicating that the 2 substrates are probably cleaved by the same enzyme. The most effective inhibitors of LH-RH degradation were found to be angiotensin-related peptides, neurotensin, bradykinin, and bacitracin. A relatively weak effect was obtained with oxytocin, enkephalin and puromycin. It is concluded that endogenous oligopeptides such as angiotensins, neurotensin, bradykinin, etc., may possibly influence H-RH degradation in the PIT and the HYP. The synthetic substrate Cys-NA may be an appropriate substrate for measuring the activity of an LH-RH-degrading peptidase, which therefore could be classified as arylamidase.
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PMID:Enzyme kinetic studies and inhibition by oligopeptides of LH-RH degradation in rat hypothalamus and pituitary. 37 17

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

The acyclic C-terminal tripeptide of oxytocin, H-Pro-Leu-Gly-NH-2, is not degraded upon incubation with human (male,female or pregnant female) plasma or serum for 1hr at 37 degrees. However, the sera of other species tested, including rat, chicken and carp, degrade this tripeptide 100%, 4% and 30%, respectively, in 1 hr, as determined by quantitative amino acid analysis of released products. Among the species studied there seems to exist a correlation between the anatomic development of the pars intermedia and the ability of the serum to hydrolyze H-Pro-Leu-Gly-NH-2, which has been proposed to be a MSH-release-inhibiting factor. The only identified degradation products are Pro, Leu and H-Gly-NH-2 with no detectable levels of H-Leu-Gly-NH2. The dipeptides H-Leu-Gly-NH-2 and H-Pro-Leu-OH are each cleaved at similiar rates in either human or rat serum, although the rate of hydrolysis of both peptides is lower in human than in rat. Thus, it does not appear that the dipeptide, H-EU-Gly-NH-2, can accumulate as one of the breakdown products of the tripeptide. The arylamidase present in rat serum has different characteristics from the enzyme in rat brain which can degrade H-Pro-Leu-Gly-NH-2.
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PMID:Significant differences in the degradation of pro-leu-gly-nH2 by human serum and that of other species (38484). 116 15