Browsing by Subject "Blood serum"

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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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    The level of aryl acylamidase activity displayed by human butyrylcholinesterase depends on its molecular distribution.
    (Elsevier, 2008-09-25) Montenegro Arce, María Fernanda; Moral Naranjo, M. T.; Páez de la Cadena, M.; Muñoz Delgado, Encarnación; Vidal, C. J.; Campoy Menéndez, Francisco Javier; Bioquímica y Biología Molecular A
    Butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) display both esterase and aryl acylamidase (AAA) activities. Their AAA activity can be measured using o-nitroacetanilide (ONA). In human samples depleted of acetylcholinesterase, we noticed that the ratio of amidase to esterase activities varied depending on the source, despite both activities being due to BuChE. Searching for an explanation, we compared the activities of BuChE molecular forms in samples of human colon, kidney and serum, and observed that BuChE monomers (G1) hydrolyzed o-nitroacetanilide much faster than tetramers (G4). This fact suggested that association might cause differences in the AAA site between single and polymerized subunits. This and other post-translational modifications in BuChE subunits probably determine their level of AAA activity. The higher amidase activity of monomers could justify the presence of single BuChE subunits in cells as a way to preserve the AAA activity of BuChE, which could be lost by oligomerization.