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

Through a series of kinetic studies involving the inactivation effects of diisopropylfluorophosphate, an affinity label that modifies the active site serine residue involved in the mechanism of action, it has been firmly established that carboxypeptidase P (CPP) requires a serine residue for catalytic activity. The essential kinetic parameters were determined to be 1.33 mM for the apparent dissociation constant with a limiting half-life of inactivation of 20.1 min. Structural elucidation of the primary amino acid sequence surrounding the essential serine, and comparing that with the reactive site of carboxypeptidase Y (CPY), revealed a significant degree of homology at the active site between these two enzymes. These regions, however, were quite divergent from other known serine proteases, leading to the speculation that these serine exopeptidases may comprise a unique family in the overall classification of serine proteases. It was established that CPY could be inactivated with either of the classic histidine affinity labels tosylphenylalanylchloromethyl ketone (TPCK) or carbobenzoxyphenylalanylchloromethyl ketone (ZPCK) with Ki's of 1.2 and 12.8 microM, respectively. This is in marked contrast to CPP, which was unaffected by saturating levels of the known histidine affinity labels, TPCK, tosyllysylchloromethyl ketone, or ZPCK. This point may be a significant element in differentiating specificity among these two serine proteases. Further investigation into the structural nature of CPP revealed that it is a glycoprotein with a single site of carbohydrate attachment. In addition, the carbohydrate moiety itself appears to contribute 1217 Da to the overall molecular weight and it is characterized as an asparagine linked high mannose type. This is significantly different from CPY with its four sites of carbohydrate attachment contributing approximately 17% to its molecular weight.
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PMID:Structural determination of the essential serine and glycosylation sites of carboxypeptidase P. 157 19

Excitatory amino acid (EAA) receptor-mediated events have recently been implicated in dopaminergic mechanisms of neurotoxicity. 2,4,5-Trihydroxyphenylalanine (6-hydroxy-DOPA, TOPA), the ortho-hydroxylated derivative of the dopamine precursor 2,4-dihydroxyphenylalanine (L-DOPA), has recently been reported to have neurotoxic properties which are blocked by CNQX, a specific antagonist of the AMPA class of non-N-methyl-D-aspartate (non-NMDA) EAA receptors. We report here that 6-hydroxy-DOPA is a selective displacer of [3H]AMPA binding in rodent brain. 6-Hydroxy-DOPA was as potent as kainate in displacing [3H]AMPA binding, with an IC50 value of 32 microM. Ineffective displacers of [3H]AMPA binding included dopamine, 6-hydroxydopamine, L-DOPA, D-DOPA, carbidopa, DOPAC, beta-methylamino-L-alanine, 2,4-dihydroxyphenylacetyl-L-asparagine, homogentisic acid, 2,4-dihydroxyphenylacetic acid, amantadine, and threo-DOPS. 6-Hydroxy-DOPA (100 microM) also displaced 20% of [3H]kainate binding, but did not displace binding to NMDA, phencyclidine (PCP), or dopaminergic (D1 and D2) receptors. These data raise the possibility that 6-hydroxy-DOPA or another abnormal metabolite of L-DOPA could act as an excitotoxic agent via action at AMPA receptors. Given that non-NMDA receptors are postulated to play a role in neurotoxic events, these data provide an additional mechanism via which EAA receptor-mediated events could produce neurodegeneration in areas of brain with dopaminergic innervation.
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PMID:2,4,5-Trihydroxyphenylalanine (6-hydroxy-dopa) displaces [3H]AMPA binding in rat striatum. 166 20

Four kinds of heteromeric N-methyl-D-aspartate (NMDA) receptor channels, the epsilon 1/zeta 1, epsilon 2/zeta 1, epsilon 3/zeta 1 and epsilon 4/zeta 1 channels, were expressed in Xenopus oocytes and their sensitivities to various non-competitive antagonists were examined. The epsilon 1/zeta 1 and epsilon 2/zeta 1 channels were more sensitive to (+)MK-801 (dizocilpine) than the epsilon 3/zeta 1 and epsilon 4/zeta 1 channels, whereas the sensitivities to phencyclidine (PCP), ketamine and N-allylnormetazocine (SKF-10,047) were only slightly variable among the four epsilon/zeta channels. Furthermore, the replacement by glutamine or arginine of the conserved asparagine residue in segment M2 of the epsilon 2 and zeta 1 NMDA receptor channel subunits reduced the sensitivities to PCP, ketamine and SKF-10,047, though to different extents. These results, together with previous findings, suggest that these non-competitive antagonists as well as (+)MK-801 and Mg2+ act on a common site.
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PMID:Different sensitivities of NMDA receptor channel subtypes to non-competitive antagonists. 834 8

1. Phencyclidine (PCP) is an inhibitor of the nicotinic acetylcholine receptor (AChR) with characteristics of an open-channel blocker. The location of PCP binding site on the AChR molecule is unknown. 2. PCP inhibits the AChR from electric organ with a higher potency than muscle AChR. To find the molecular basis of this difference, we expressed the two native and six hybrid receptors, and two receptors containing mutated mouse gamma subunits in Xenopus laevis oocytes. The inhibition of ACh-induced current in these receptors by PCP was studied using whole-cell voltage-clamp. All hybrid receptors generated robust ACh-induced currents, while incomplete receptors (gamma-less or delta-less) did not. 3. PCP potency was higher on hybrids containing Torpedo beta and gamma subunits regardless of the alpha and delta subunit origin. A mouse gamma subunit containing the asparagine 6' to the serine mutation in the M2 segment conferred a high sensitivity to PCP. 4. These results support the conclusion that the amino acid residues at the position 6' of the M2 segments contribute to the PCP potency difference between Torpedo and mouse receptors. 5. Another noncompetitive inhibitor of the AChR, the cembranoid eupalmerin acetate (EUAC), also inhibited the electric organ receptor with a somewhat higher potency than muscle AChR. However, the IC50 values for EUAC inhibition of hybrid receptors did not follow the pattern observed for PCP. Therefore, these two inhibitors interact differently with the AChR molecule.
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PMID:Determinants of phencyclidine potency on the nicotinic acetylcholine receptors from muscle and electric organ. 1045 35

Neuroprotective and biobehavioral properties of a series of novel open chain MK-801 analogs, as well as their structure-activity relationships have been investigated. Three groups of compounds were synthesized: monobenzylamino, benzhydrylamino, and dibenzylamino (DBA) analogs of MK-801. It was revealed that DBA analogs exhibit pronounced glutamate-induced calcium uptake blocking properties and anti-NMDA activity. The hit compound of DBA series, NT-1505, was investigated for its ability to improve cognition functions in animal model of Alzheimer's disease type dementia, simulated by treating animals with cholinotoxin AF64A. The results from an active avoidance test and a Morris water maze test showed that experimental animals, treated additionally with NT-1505, exhibited much better learning ability and memory than the control group (AF64A treated) and close to that of the vehicle group of animals (treated with physiological solution). Study of NT-1505 influence on locomotor activity revealed that it is characterized by a spectrum of behavioral activity radically different from that of MK-801, and in contrast to the latter one does not produce any psychotomimetic side effects in the therapeutically significant dose interval. The computed docking of MK-801 and its flexible analogs on the NMDA receptor elucidated the crucial role of the hydrogen bond formed between these compounds and the asparagine residue for magnesium binding in the NMDA receptor. It was suggested that strong hydrophobic interaction between MK-801 and the hydrophobic pocket in the NMDA receptor-channel complex determines much higher irreversibility of this adduct compared to the intermediates formed between this site and Mg ions or flexible DBA derivatives, which might explain the absence of PCP-like side effects of the latter compounds.
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PMID:Neuroprotective and cognition-enhancing properties of MK-801 flexible analogs. Structure-activity relationships. 1146 74

A stator is proposed as necessary to prevent futile rotation of the F(1) catalytic sector of mitochondrial ATP synthase (mtATPase) during periods of ATP synthesis or ATP hydrolysis. Although the second stalk of mtATPase is generally believed to fulfil the role of a stator capable of withstanding the stress produced by rotation of the central rotor, there is little evidence to directly support this view. We show that interaction between two candidate proteins of the second stalk, OSCP and subunit b, fused at their C-termini to GFP variants and assembled into functional mtATPase can be monitored in mitochondria using fluorescence resonance energy transfer (FRET). Substitution of native OSCP with a variant containing a glycine 166 to asparagine (G166N) substitution yielded a metastable complex. In contrast to the enzyme containing native OSCP, FRET could be irreversibly lowered for the enzyme containing G166N at a rate that correlated closely with the rate of enzyme activity (ATP hydrolysis). The non-hydrolysable ATP analogue, AMP-PCP did not have this effect. We conclude that two candidate proteins of the stator stalk, OSCP and b, are subject to stresses during enzyme catalytic activity commensurate with their role as a part of a stator stalk.
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PMID:FRET reveals changes in the F1-stator stalk interaction during activity of F1F0-ATP synthase. 1467 Jun 7