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)

We have previously demonstrated in permeabilized rat pancreatic acini that the existence of two affinity states of the pancreatic cholecystokinin (CCK) receptor seen in intact cells depends on the presence of ATP. In the present study, we demonstrate that this effect of ATP is mediated by the enzyme nucleoside diphosphate kinase (NDPK). Northern blot hybridization analysis demonstrated NDPK mRNA in pancreas. Furthermore, pancreatic membranes possessed NDPK activity, which transferred high-energy phosphate groups to [8-3H]GDP. This enzyme also utilized UTP and ITP as a source of gamma-phosphate for GTP formation while guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) was formed in the presence of adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S). However, adenylyl (beta, gamma-methylene)-diphosphate (AMP-PCP) did not serve as a substrate for NDPK. Analysis of 125I-Bolton-Hunter-labeled CCK octapeptide ([125I]BH-CCK-8) binding data in the absence of nucleotides was consistent with a single affinity state with dissociation constant (Kd) equal to 80 pM and maximal binding equal to 50.8 fmol/mg. ATP, UTP, ITP, ATP gamma S, and GTP gamma S all induced two CCK binding affinity states, which in the presence of 1 mM ATP were Kd = 74 pM for high-affinity sites and Kd = 4.3 nM for low-affinity sites: AMP-PCP did not induce two affinity states. GDP at 10 microM had no effect on CCK binding but potentiated the effect of ATP. GTP gamma S, in addition to inducing high- and low-affinity states, also elicited a significant concentration-dependent reduction in the total number of measurable CCK receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nucleoside diphosphate kinase associated with rat pancreatic membranes regulates CCK receptor affinity. 797 49

Cholecystokinin (CCK) receptors on rat pancreatic acinar cells display two binding affinity states in the presence of adeninine and guanine triphosphates with the effect of ATP mediated by the enzyme nucleoside diphosphate kinase. To determine whether this behavior was intrinsic to a single receptor protein we studied the binding affinity of CHO cells stably transfected with a cloned rat CCKA receptor. 125I-CCK binding to intact cells at 37 degrees C revealed two affinity states for CCK of Kd values 20 pM and 2.4 nM. Membranes prepared from these cells displayed a single affinity state for CCK but two affinity states could be restored in the presence of GTP[gamma S], ATP and ATP[gamma S] but not AMP-PCP. ATP and ATP[gamma S] but not AMP-PCP were substrates for nucleoside diphosphate kinase present in CHO cell membranes and transferred their terminal phosphate to GDP. These findings indicate that the interconvertible affinity states of the CCK receptor are inherent in a single receptor protein and that nucleoside diphosphate kinase mediates the effect of ATP to regulate these two affinity states.
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PMID:Nucleotides regulate the binding affinity of the recombinant type A cholecystokinin receptor in CHO K1 cells. 885 9

The role of nucleoside diphosphate kinase (NDKP), which converts GDP to GTP, in the coupling of mu-opioid receptors to G protein was investigated in membranes of Chinese hamster ovary cells stably transfected with the cloned rat mu-opioid receptor (rmor). Endogenous NDPK activity in membranes was determined to be 0.60+/-0.02 micromol/mg protein/30 min UDP (at 10 mM), a competitive substrate of NDPK for GDP with no effect on guanine nucleotide binding to G proteins, reduced basal [35S]GTPgammaS binding and unmasked morphine-stimulated [35S]GTPgammaS binding to pertussis toxin-sensitive G proteins, indicating that [35S]GTPgammaS binding to NDPK accounts for part of its high basal binding. UDP increased the extent of morphine-induced increase in [35S]GTPgammaS binding in the presence of GDP, most likely by reducing basal binding and inhibiting conversion of GDP to GTP. ATP greatly reduced morphine-induced increase in [35S]GTPgammaS binding, whereas AMP-PCP (adenylyl-(beta,gamma-methylene)-diphosphoate tetralithium salt), which cannot serve as the phosphate donor for NDPK, did not, demonstrating that effects of ATP is mediated by the NDPK product GTP. In addition, GDP and ATP increased the Kd and lowered the Bmax of the agonist [3H]DAMGO ([D-Ala2,N-Me-Phe4,Gly5ol]-Enkephalin) for the mu-opioid receptor and GDP alone increased Kd, most likely through their conversion to GTP by NDPK. Addition of exogenous NDPK enhanced the inhibitory effects of GDP and combined GDP and ATP on [3H]DAMGO binding. Thus, NDPK appears to play a role in modulating signal transduction of and agonist binding to mu-opioid receptors.
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PMID:Nucleoside diphosphate kinase associated with membranes modulates mu-opioid receptor-mediated [35S]GTPgammaS binding and agonist binding to mu-opioid receptor. 1045 35