Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.11 (CD10)
 9,792 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of a number of peptide-degrading enzymes were compared in homogenates of GH3 cells and rat anterior pituitaries. The enzymes studied were prolyl endopeptidase (EC 3.4.21.26), a soluble metalloendopeptidase, pyroglutamyl peptide hydrolase (EC 3.4.11.8), a multicatalytic protease complex, cathepsin B (EC 3.4.22.1), cathepsin D (EC 3.4.23.5), aminopeptidase (EC 3.4.11.2), and a membrane-bound neutral metalloendopeptidase (EC 3.4.24.11). Specific substrates were used to measure the activities, and active-site-directed inhibitors were used to verify the identities of the enzymes studied. Of the two lysosomal enzymes studied, cathepsin B, the enzyme with the highest activity in both preparations, had 5 times the activity in GH3 cell homogenates as in anterior pituitary homogenates. Cathespin D had a somewhat higher activity in the anterior pituitary homogenates than in the GH3 cell homogenates. Soluble metalloendopeptidase and prolyl endopeptidase, both cytoplasmic enzymes, had about twice the activity in GH3 cell homogenates as in anterior pituitary homogenates. Membrane-bound neutral metalloendopeptidase in the GH3 cell homogenates had 25% of the activity of the anterior pituitary homogenates. Of the two TRH-degrading enzymes, the activity of prolyl endopeptidase in GH3 cell homogenates was about 25 times higher than that of pyroglutamyl peptide hydrolase. Since the secretory function of the pituitary is in part controlled by neuropeptides, the knowledge of the enzyme profiles of the GH3 cells and the anterior pituitary should be of value in studying the metabolism of neuropeptides and peptide hormones in these systems.
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PMID:Peptide-degrading enzymatic activities in GH3 cells and rat anterior pituitary homogenates. 636 4

Pro-thyrotropin-releasing hormone (proTRH) is the precursor to thyrotropin-releasing hormone (TRH; pGlu-His-Pro-NH2), the hypothalamic releasing factor that stimulates synthesis and release of thyrotropin from the pituitary gland. Five copies of the TRH progenitor sequence (Gln-His-Pro-Gly) and seven cryptic peptides are formed following posttranslational proteolytic cleavage of the 26-kDa rat proTRH precursor. The endopeptidase(s) responsible for the physiological conversion of proTRH to the TRH progenitor form is currently unknown. We examined the in vitro processing of [3H]leucine-labeled or unlabeled proTRH by partially purified recombinant PC1. Recombinant PC1 processed the 26-kDa TRH precursor by initially cleaving the prohormone after the basic amino acid at either position 153 or 159. Based on the use of our well-established antibodies, we propose that the initial cleavage gave rise to the formation of a 15-kDa N-terminal peptide (preproTRH25-152 or pre-proTRH25-158) and a 10-kDa C-terminal peptide (pre-proTRH154-255 or preproTRH160-255). Some initial cleavage occurred after amino acid 108 to generate a 16.5-kDa C-terminal peptide. The 15-kDa N-terminal intermediate was further processed to a 6-kDa peptide (prepro-TRH25-76 or preproTRH25-82) and a 3.8-kDa peptide (preproTRH83-108), whereas the 10-kDa C-terminal intermediate was processed to a 5.4-kDa peptide (prepro-TRH206-255). The optimal pH for these cleavages was 5.5. ZnCl2, EDTA, EGTA, and the omission of Ca2+ inhibited the formation of pYE27 (preproTRH25-50), one of the proTRH N-terminal products, by 48, 82, 72, and 45%, respectively. This study provides evidence, for the first time, that recombinant PC 1 enzyme can process proTRH to its predicted peptide intermediates.
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PMID:Pro-thyrotropin-releasing hormone processing by recombinant PC1. 759 40

Recent evidence supports the hypothesis of a direct action of LHRH at the level of the prostate. Since peptidases able to degrade the hormone are present in several LHRH target structures, it was deemed of interest to investigate whether the prostate of adult normal male rats might possess LHRH degrading activities (LHRH-DA). Through the use of RP-HPLC, it has been observed that LHRH-DA is present in the soluble fraction of the rat ventral prostate homogenate, and is able to hydrolyze synthetic LHRH and to generate fragments 1-3 and 1-5 of the decapeptide. The degradation of [pGlu-3H]LHRH is inhibited by LHRH itself, and affected by several LHRH agonists and antagonists with different kinetics and potencies. TRH, the enkephalin analog [D-Ala2-D-Leu5]enkephalin and rat prolactin do not inhibit the degradation of [pGlu-3H]LHRH by the soluble fraction of prostate homogenate; on the contrary, this is inhibited by graded doses of somatostatin. The prostatic LHRH-DA is also inhibited, in a dose dependent manner, by bacitracin, serine protease inhibitors (diisopropylfluorophosphate and phenylmethansulfonylfluoride), the metal chelating agent EDTA, HgCl2, and dithiothreitol. No inhibitory effect on [pGlu-3H]LHRH hydrolysis was observed after incubation of the prostatic extract in the presence of captopril. The prostatic LHRH-DA seems to be different from that present in other tissues of the rat (e.g., hypothalamus, pituitary, gonads), and to be decreased by castration performed 3 weeks before. These results suggest that (1) an LHRH-DA is found in the soluble fraction of rat prostate homogenate; (2) this enzymatic activity exhibits the characteristics of a metallo- and thiol-dependent neutral endopeptidase; (3) it appears to be different from similar hydrolytic activities found in other tissues; and (4) it is influenced by the hormonal milieu, since castration causes a significant decrease of its activity.
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PMID:Characterization of a soluble LHRH-degrading activity in the rat ventral prostate. 825 44

Gonad and thyroid dysfunctions are often observed in human and experimental models during african trypanosomiasis. The enzymatic activity of components released by the trypanosomes towards peptide hormones (e.g. GnRH, TRH) have consequently been studied. The incubation products of GnRH by (i) healthy or infested rat serum: (ii) trypanosomal components released by using a specific procedure; (iii) infested and normal rat brain extracts have been analysed by RP-HPLC fractionation. The peptide cleavage has been assessed by determination of either the amino acid compositions or relative molecular weight (by FAB mass spectrometry) of the different resolved HPLC fractions. Different protease inhibitors and a reducing agent have also been tested and a serine, cation-sensitive, thiol-dependent endopeptidase activity has been predominantly identified to be released by the trypanosomes in host circulation. It has been shown that the peptidase activity(ies) is(are) able to: (i) degrade the peptide hormones (GnRH, TRH) considered as important neuromodulators and neurotransmitters; (ii) generate an unusual N-terminal tetrapeptide (GnRH1-4) appearing to be still active towards the gonadal hypothalamo-pituitary axis.
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PMID:Unusual cleavage of peptidic hormones generated by trypanosome enzymes released in infested rat serum. 845 88

Prolyl endopeptidase has been predominantly described as a cytosolic activity capable of cleaving a number of important neuropeptides (including TRH, LHRH, Bradykinin, Angiotensin, Substance P, Neurotensin, Oxytocin and Vasopressin) on the carboxy side of proline. In this paper, we report, for the first time, on the complete purification and characterization of a membrane-bound form of prolyl endopeptidase. This novel activity has been isolated from the synaptosomal (plasma membranes) membranes of bovine brain. Following gel filtration, hydroxylapatite and hydrophobic interaction chromatographies, the prolyl endopeptidase activity was purified 1400-fold with a 23% recovery of activity. The enzyme was shown to have a relative molecular mass of 87 kDa and a Km of 60 microM for its specific fluorimetric substrate, Z-GlyProMCA. The purified enzyme demonstrated a relatively broad substrate specificity and a relatively high affinity for proline-containing neuropeptides. It was shown to be inhibited by certain thiol-protease inhibitors and by the metal chelator, 1,10-phenanthroline, thus possibly classifying it as a 'thimet' activity. The purified particular form of proyl endopeptidase displayed a similar substrate specificity to the previously reported cytosolic forms of the enzyme. However, there were differences between the two forms in term of their sensitivity to inhibitors, their affinities for the peptide substrates and their relative molecular masses. The different subcellular location (i.e. the synaptosomal membrane) of the particulate prolyl endopeptidase is also of potential physiological significance given that here it is more likely to come in contact with the vesicle-bound neuropeptides than is its cytosolic counterpart.
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PMID:Purification and characterization of a novel membrane-bound form of prolyl endopeptidase from bovine brain. 902 55

Aminopeptidase N (APN) and neprilysin (NEP) inactivate neuropeptides released into the brain extracellular fluid. We previously showed that the expression of pyroglutamyl peptidase II (PPII), the TRH degrading ecto-enzyme, is regulated in rat brain by amygdaline kindling, a paradigm that activates neuronal pathways in the limbic system increasing the expression of several neuropeptides including TRH and opioids. To understand the specificity of this phenomenon, we studied APN and NEP expression in brains of partially or fully kindled rats (stage II and V), sacrificed 6 h after last stimulus, compared with sham-operated animals. In situ hybridization analysis of NEP mRNA levels showed decreased expression at stage II in CA1, CA2, olfactory tubercle and medial mammillary nucleus, and increased at stage V in CA1 and CA2 cells. These changes were specific for the ipsilateral side. APN mRNA levels, semi-quantified by RT-PCR, were decreased at stage II and increased at stage V, in frontal cortex-olfactory tubercle, and hippocampus. NEP and APN enzymatic activities, determined by fluorometric assays, followed similar variations to their respective mRNA levels. The coordinated changes (in some regions) of NEP and APN expression were opposite to those previously observed for PPII mRNA and activity levels in limbic regions. These results demonstrate that expression of ectopeptidases can be regulated when peptide neurons are activated and, that regulation is enzyme-, region-, and stage-specific.
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PMID:Stage-specific modulation of neprilysin and aminopeptidase N in the limbic system during kindling progression. 1795 34