Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. A method for the preparation of brush border from rabbit kidneys is described. Contamination by other organelles was checked by electron microscopy and by the assay of marker enzymes and was low. 2. Seven enzymes, all hydrolases, were substantially enriched in the brush-border preparation and are considered to be primarily located in this structure. They are: alkaline phosphatase, maltase, trehalase, aminopeptidase A, aminopeptidase M, gamma-glutamyl transpeptidase and a neutral peptidase assayed by its ability to hydrolyse [(125)I]iodoinsulin B chain. 3. Adenosine triphosphatases were also present in the preparation, but showed lower enrichments. 4. Alkaline phosphatase was the most active phosphatase present in the preparation. The weak hydrolysis of AMP may well have been due to this enzyme rather than a specific 5'-nucleotidase. 5. The two disaccharidases in brush border were distinguished by the relative heat-stability of trehalase compared with that of maltase. 6. The individuality of the four peptidases was established by several means. The neutral peptidase and aminopeptidase M, both of which can attack insulin B chain, differed not only in response to inhibitors and activators but also in the inhibitory effect of a guinea-pig antiserum raised to rabbit aminopeptidase M. This antiserum inhibited both the purified and the brush-border activities of aminopeptidase M. The neutral peptidase and gamma-glutamyl transpeptidase were unaffected but aminopeptidase A was weakly inhibited. The characteristic responses to Ca(2+) and serine with borate served to distinguish aminopeptidase A and gamma-glutamyl transpeptidase from other peptidases. 7. No dipeptidases, tripeptidases or carboxypeptidases were identified as brush-border enzymes. 8. Incubation of brush border with papain released almost all the aminopeptidase M activity but only about half the activities of maltase, gamma-glutamyl transpeptidase and aminopeptidase A. No release of alkaline phosphatase, trehalase or the neutral peptidase was observed.
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PMID:Studies on the enzymology of purified preparations of brush border from rabbit kidney. 414 72

Incubation of pig kidney microvillar membranes with Bacillus thuringiensis or Staphylococcus aureus phosphatidylinositol-specific phospholipase C (PI-PLC) resulted in the release of a number of glycosyl-phosphatidylinositol (GPI)-anchored hydrolases, including alkaline phosphatase (EC 3.1.3.1), amino-peptidase P (EC 3.4.11.9), membrane dipeptidase (EC 3.4.13.19), 5'-nucleotidase (EC 3.1.3.5) and trehalase (EC 3.2.1.28). Of these five ectoenzymes only for membrane dipeptidase was there a significant (approx. 100%) increase in enzymic activity upon release from the membrane. Maximal activation occurred at a PI-PLC concentration 10-fold less than that required for maximal release. In contrast solubilization of the membranes with n-octyl beta-D-glucopyranoside had no effect on the enzymic activity of membrane dipeptidase. A competitive e.l.i.s.a. with a polyclonal antiserum to membrane dipeptidase indicated that the increase in enzymic activity was not due to an increase in the amount of membrane dipeptidase protein. Although PI-PLC cleaved the GPI anchor of the affinity-purified amphipathic form of pig membrane dipeptidase there was no concurrent increase in enzymic activity. In the absence of PI-PLC, membrane dipeptidase in the microvillar membranes hydrolysed Gly-D-Phe with a Km of 0.77 mM and a Vmax. of 602 nmol/min per mg of protein. However, in the presence of a concentration of PI-PLC which caused maximal release from the membrane and maximal activation of membrane dipeptidase the Km was decreased to 0.07 mM while the Vmax. remained essentially unchanged at 624 nmol/min per mg of protein. Overall these results suggest that cleavage by PI-PLC of the GPI anchor on membrane dipeptidase may relax conformational constraints on the active site of the enzyme which exist when it is anchored in the lipid bilayer, thus resulting in an increase in the affinity of the active site for substrate.
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PMID:Activation of the glycosyl-phosphatidylinositol-anchored membrane dipeptidase upon release from pig kidney membranes by phospholipase C. 798 Apr 26