Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
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Drug
Enzyme
Compound
Query: EC:3.1.3.5 (
5'-nucleotidase
)
3,167
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
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.
...
PMID:Activation of the glycosyl-phosphatidylinositol-anchored membrane dipeptidase upon release from pig kidney membranes by phospholipase C. 798 Apr 26
Several mammalian enzymes are anchored to the outer surface of the plasma membrane by a covalently attached glycosyl-phosphatidylinositol (GPI) structure. These include acetylcholinesterase, alkaline phosphatase,
membrane dipeptidase
and
5'-nucleotidase
. All GPI anchors determined to date have the conserved core structure ethanolamine-PO4-6Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcNH2 alpha 1-6myo-inositol-1-PO4- lipid. In most mammalian GPI anchors the lipid is 1-alkyl-2-acyl-glycerol, although in porcine
membrane dipeptidase
it is diacylglycerol. Attached to the conserved core are various side chain residues that appear to be either protein- or tissue-specific. In addition to membrane attachment, a GPI anchor may confer additional properties on the protein, such as the susceptibility to cleavage by phospholipases and the potential to cluster in detergent-insoluble domains. GPI anchors can also act as intracellular targeting signals, in transmembrane signalling, in the clathrin-independent endocytic process of potocytosis and as hormone mediators. Thus, a GPI anchor can confer additional properties on enzymes that may be important in their physiological and pathophysiological functioning.
...
PMID:Glycosyl-phosphatidylinositol anchored membrane enzymes. 943 83
