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 microsomal fraction of rabbit liver contains an endopeptidase that cleaves synthetic peptides that mimic the amino acid sequences of the processing sites of many proproteins, including the vitamin K-dependent proteins. The endopeptidase (M(r) 69,000) was extracted from liver microsomes with 1% Lubrol and purified about 2,700-fold. The substrate employed for isolation and characterization of the enzyme was the decapeptide acetyl-Ala-Arg-Val-Arg-Arg-Ala-Asn-Ser-Phe-Leu (prothrombin peptide), in which hydrolysis occurred on the carboxyl side of the paired Arg-Arg residues. The purified enzyme, whose activity was enhanced 1.8-fold by 0.1 mM CoCl2, has a Km = 80 microM and Vmax = 21,000 nmol.min-1.mg-1 and a pH optimum of 8.7. Proteolytic cleavage of decapeptide substrates was dependent on an arginine residue at positions P1 and P4. The enzyme was completely inhibited by EDTA and 1,10-phenanthroline as well as by p-chloromercuriphenylsulfonic acid and Hg2+. Inhibitors of serine proteases and cysteine proteases had no effect. Based on the substrate preference, the endopeptidase appears to be a good candidate for the enzyme responsible for the precursor processing of the vitamin K-dependent proteins and a number of other proproteins that are synthesized via the secretory pathway in liver and other tissues.
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PMID:A microsomal endopeptidase from liver with substrate specificity for processing proproteins such as the vitamin K-dependent proteins of plasma. 131 98

Carboxypeptidase M, a plasma membrane-bound enzyme, is present in many human organs and differs from other carboxypeptidase that cleave basic COOH-terminal amino acids. Cultured Madin-Darby canine kidney (MDCK) distal tubular cells contain a kininase I-type enzyme that inactivates bradykinin by releasing Arg9. We found the properties of this kininase to be identical with carboxypeptidase M. In fractionated cells, carboxypeptidase activity sediments with membranes; and detergents, trypsin, and phosphatidylinositol-specific phospholipase C solubilize it, similar to results with human placental carboxypeptidase M. Ten microM 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid and 1 mM o-phenanthroline inhibit, whereas 1.0 mM CoCl2 activates the enzyme. It has a neutral pH optimum and cleaves COOH-terminal Arg or Lys in bradykinin and in shorter peptides. The relative hydrolysis rates of peptides in the presence or absence of 1 mM CoCl2 were similar to those obtained with human carboxypeptidase M. The carboxypeptidase in MDCK cells (54 kDa) cross-reacts with antibodies to human carboxypeptidase M in Western blotting, but not with antibodies to plasma carboxypeptidase N. The enzyme is a glycoprotein; chemical deglycosylation reduced the size to 48 kDa. The presence of the enzyme on the cell membrane of MDCK cells was also shown with transmission electron microscopy using immunogold, which indicated that the enzyme is on the apical side. In addition, MDCK cells contain neutral endopeptidase 24.11 (enkephalinase) and prolylcarboxypeptidase (angiotensinase C) activities. Partitioning of solubilized carboxypeptidase M into Triton X-114 and water indicates that trypsin and phospholipase C remove a hydrophobic tail, while detergent solubilization leaves the hydrophobic moiety intact. Labeling of MDCK cells with [3H]ethanolamine resulted in the synthesis of radiolabeled carboxypeptidase M as determined by immunoprecipitation and fluorography. Thus, MDCK cells contain membrane-bound carboxypeptidase M, which is anchored to the plasma membrane via phosphatidylinositol-glycan. As a major kininase of the distal tubules, it may regulate salt and water excretion.
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PMID:Carboxypeptidase M in Madin-Darby canine kidney cells. Evidence that carboxypeptidase M has a phosphatidylinositol glycan anchor. 239 13

Although kinins have been reported to affect cerebral vascular tone and permeability, their actions are not potentiated by angiotensin converting enzyme inhibitors. To investigate cerebral vascular kinin metabolism, porcine cerebral microvessels were isolated by differential sieving and centrifugation and characterized by microscopic examination and marker enzyme enrichment. Purified microvessels contained a membrane-bound carboxypeptidase which hydrolyzed the C-terminal Phe-Arg bond of both kallidin and bradykinin. Hydrolysis was optimal at pH 7.0, was activated more than 300% by 0.1 mM CoCl2, and was inhibited by o-phenanthroline and the carboxypeptidase N (EC 3.4.17.3) inhibitor DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid (MERGETPA) (IC50 = 2 microM). Conversely, inhibitors of angiotensin I converting enzyme (captopril), neutral endopeptidase (phosphoramidon), post proline cleaving enzyme (Z-Pro-prolinal), dipeptidyl(amino)peptidase IV (diprotin A) and amino-peptidase M (amastatin) had no effect. When the rates of C-terminal hydrolysis of kallidin by detergent-solubilized cerebral microvasculature were determined over a range of substrate concentrations (16.6 to 250 microM), the Km and Vmax values obtained were 26.0 +/- 3.0 microM and 14.7 +/- 1.3 nmol/min/ml (N = 4) respectively. These data suggest that a cerebral microvascular carboxypeptidase may play a role in vivo in modulating the effects of kinins on cerebral blood flow and permeability and in preventing circulating kinins from crossing the blood-brain barrier.
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PMID:Kallidin and bradykinin metabolism by isolated cerebral microvessels. 339 72