Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.16.2 (PCP)
 3,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A comprehensive survey of 11 peptidases, all of which are markers for renal microvillar membranes, has been made in membrane fractions prepared from pig choroid plexus. Two fractionation schemes were explored, both depending on a MgCl2-precipitation step, the preferred one having advantages in speed and yield of the activities. The specific activities of the peptidases in the choroid-plexus membranes were, with the exception of carboxypeptidase M, lower than in renal microvillar membranes: those of aminopeptidase N, peptidyl dipeptidase A ('angiotensin-converting enzyme') and gamma-glutamyltransferase were 3-5-fold lower, those of aminopeptidase A and endopeptidase-24.11 were 12-15 fold lower, and those of dipeptidyl peptidase IV and aminopeptidase W were 50-70-fold lower. Carboxypeptidase M had a similar activity in both membranes. Alkaline phosphatase and (Na+ + K+)-activated ATPase were more active in the choroid-plexus membranes. No activity for microsomal dipeptidase, aminopeptidase P and carboxypeptidase P could be detected. Six of the peptidases and (Na+ + K+)-activated ATPase were also studied by immunoperoxidase histochemistry at light- and electron-microscopic levels. Endopeptidase-24.11 and (Na+ + K+)-activated ATPase were uniquely located on the brush border, and the other two peptidases appeared to be much more abundant on the endothelial lining of microvessels. Dipeptidyl peptidase IV and aminopeptidase W were also detected in microvasculature. Pial membranes associated with the brain and spinal cord also stained positively for endopeptidase-24.11, aminopeptidase N and peptidyl dipeptidase A. The immunohistochemical studies indicated the subcellular fractionation did not discriminate between membranes derived from epithelial cells (i.e. microvilli) and those from endothelial cells. The possible significance of these studies in relation to neuropeptide metabolism and the control of cerebrospinal fluid production is discussed.
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PMID:Membrane peptidases in the pig choroid plexus and on other cell surfaces in contact with the cerebrospinal fluid. 265 79

Two intestinal brush border membrane carboxypeptidases were found to participate in the sequential digestion of proline-containing peptides representing a novel mechanism of hydrolysis from the COOH terminus. NH2-blocked prolyl tripeptides were rapidly hydrolyzed by either brush border membrane angiotensin converting enzyme (ACE, dipeptidyl carboxypeptidase, E.C. 3.4.15.1) or carboxypeptidase P (E.C.3.4.12-) depending on the position of the proline residue. Furthermore, these two enzymes were found to participate in a concerted manner to sequentially degrade larger proline-containing pentapeptides from the COOH terminus. A brush border membrane associated neutral endopeptidase also participated in the hydrolysis of the prolyl pentapeptides. During in vivo intestinal perfusion, the NH2-blocked prolyl peptides were degraded and their constituent amino acids efficiently absorbed by the intestine. Furthermore, hydrolysis and absorption of these peptides could be dramatically suppressed by low concentrations of captopril, a specific inhibitor of ACE. These studies show that prolyl peptides are efficiently and sequentially hydrolyzed from the COOH terminus by the combined action of ACE and carboxypeptidase P, and that these enzymes may play an important role in the digestion and assimilation of proline-containing peptides.
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PMID:Digestion and assimilation of proline-containing peptides by rat intestinal brush border membrane carboxypeptidases. Role of the combined action of angiotensin-converting enzyme and carboxypeptidase P. 283 43

A proline-specific carboxypeptidase (carboxypeptidase P, EC 3.4.12.-) was identified and partially characterized in the brush border membrane fraction of rat intestinal enterocytes and shown to be distinct from pancreatic proteases. The carboxypeptidase activity of isolated brush border membranes, with Z-Gly-Pro-Leu as substrate, was 43 nmol/min/mg protein representing a 16-fold purification when compared with mucosal cell homogenates. Activity was maximal in the middle region of the small intestine, and villus cells had twice the activity of crypt cells. Carboxypeptidase activity was maximal at pH 7.0, was stimulated by divalent cations, and was inhibited by metal chelating agents, suggesting that it is a metalloenzyme. The enzyme had the highest activity with synthetic peptides containing proline penultimate to the carboxy terminus. In vivo patterns of hydrolysis and absorption of amino acids from Z-Pro-Trp were examined using an intestinal perfusion technique. These studies indicate that brush border membrane carboxypeptidase may play an important role in the digestion of proline-containing peptides and proteins.
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PMID:Identification of proline-specific carboxypeptidase localized to brush border membrane of rat small intestine and its possible role in protein digestion. 292 Jun 46