Browsing by Subject "Cholinesterases"

Now showing 1 - 3 of 3
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    Cholinesterases are down-expressed in human colorectal carcinoma
    (Springer, 2006-08-11) Montenegro Arce, María Fernanda; Ruiz Espejo, Francisco; Campoy, F. J.; Muñoz Delgado, Encarnación; Páez de la Cadena, M.; Rodríguez-Berrocal, F. J.; Vidal, C. J.; Bioquímica y Biología Molecular A
    The aberrations of cholinesterase (ChE) genes and the variation of ChE activity in cancerous tissues prompted us to investigate the expression of ChEs in colorectal carcinoma. The study of 55 paired specimens of healthy (HG) and cancerous gut (CG) showed that acetylcholinesterase (AChE) activity fell by 32% and butyrylcholinesterase (BuChE) activity by 58% in CG. Abundant AChE-H, fewer AChE-T, and even fewer AChE-R and BuChE mRNAs were observed in HG, and their content was greatly diminished in CG. The high level of the AChE-H mRNA explains the abundance of AChE-H subunits in HG, which as glycosylphosphatidylinositol (GPI)-anchored amphiphilic AChE dimers (GA2 ) and monomers (GA1) account for 69% of AChE activity. The identification of AChE-T and BuChE mRNAs justifies the occurrence in gut of A12, GH4 and PRiMA-containing GA4 AChE forms, besides GH4 , GA4 and GH1 BuChE. The down-regulation of ChEs might contribute to gut carcinogenesis by increasing acetylcholine availability and overstimulating muscarinic receptors.
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    Human butyrylcholinesterase components differ in aryl acylamidase activity
    (De Gruyter Brill, 2008-03-27) Montenegro Arce, María Fernanda; Moral Naranjo, María T.; Páez de la Cadena, María; Campoy Menéndez, Francisco Javier; Muñoz Delgado, Encarnación; Vidal, Cecilio J.; Bioquímica y Biología Molecular A
    Apart from its esterase activity, butyrylcholinesterase (BuChE) displays aryl acylamidase (AAA) activity able to hydrolyze o-nitroacetanilide (ONA) and its trifluoro-derivative (F-ONA). We report here that, despite amidase and esterase sites residing in the same protein, in human samples depleted of acetylcholinesterase the ratio of amidase to esterase activity varied depending on the source of BuChE. The much faster degradation of ONA and F-ONA by BuChE monomers (G1) of colon and kidney than by the tetramers (G4) suggests aggregation-driven differences in the AAA site between single and polymerized subunits. The similar ratio of F-ONAto butyrylthiocholine hydrolysis by serum G1 and G4 forms support structural differences in the amidase site according to the source of BuChE. The changing ratios of amidase to esterase activities in the human sources probably arise from post-translational modifications in BuChE subunits, the specific proportion of monomers and oligomers and the variable capacity of the tetramers for degrading ONA and F-ONA. The elevated amidase activity of BuChE monomers and the scant activity of the tetramers justify the occurrence of single BuChE subunits in cells as a means to sustain the AAA activity of BuChE which otherwise could be lost by tetramerization.
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    Targeting of acetylcholinesterase to lipid rafts of muscle
    (Elsevier, 2008-09-25) Moral Naranjo, M. T.; Montenegro Arce, María Fernanda; Muñoz Delgado, Encarnación; Campoy, M. J.; Vidal, C. J.; Bioquímica y Biología Molecular A
    Despite the great progress made in setting the basis for the molecular diversity of acetylcholinesterase (AChE), an explanation for the existence oftwo types of amphiphilic subunits, with and without glicosylphosphatidylinositol (GPI) (Types I and II), has not been provided yet. In searching whether, as for the deficiency of dystrophin, that of merosin (laminin- 2 chain) alters the number of caveolae in muscle, a high increase in caveolin-3 (Cav3) was observed in the Triton X-100-resistant membranes (TRM) isolated from muscle of merosin-deficient dystrophic mice (Lama2dy). The rise in Cav3 was accompanied by that of non-caveolar lipid rafts, as showed by the greater ecto-5 -nucleotidase (eNT) activity, a marker of non-caveolar rafts, in TRM of dystrophic muscle. The observation of AChE activity in TRM, the increased levels of rafts and raft-bound AChE activity in merosin-deficient muscle and the presence of phospholipase C-sensitive AChE dimers in TRM supported targeting of glypiated AChE to rafts. This issue and the involvement of TRM in conveying nicotinic receptors to the neuromuscular junction and particular muscarinic receptors to cardiac sarcolemma strongly support a role for lipid rafts in targeting ACh receptors and glypiated AChE. Their nearby location in the surface membrane may provide cells with a fine tuning for regulating cholinergic responses.