Rapid loss of ornithine decarboxylase activity during encystation of Entamoeba invadens |
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Authors: | Carlos Calvo-Méndez Julio César Villagómez-Castro Everardo López-Romero |
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Institution: | Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados, Instituto Politécnico Nacional, Mexico City, Mexico; Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Guanajuato, Mexico |
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Abstract: | Abstract Stimulation of encystation of Entamoeba invadens by incubation of trophozoites under glucose-limiting conditions brought about a dramatic fall of ornithine decarboxylase activity, a key enzyme in polyamine biosynthesis. Levels of enzyme specific activity after 24 and 48 h of encystation represented only 11% and 1.3%, respectively, of those detected at the start of incubation. Induction of encystation in the presence of exogenously added polyamines resulted in a marked reduction in cyst formation. Thus, after 72 h of incubation, 1.0 mM putrescine, 1.0 mM spermidine or 0.5 mM spermine reduced encystation by 48 to 56%. Inhibition was enhanced to 70–73% in response to a two-fold increase in the concentration of either putrescine or spermine. Our results indicate that polyamine biosynthesis from ornithine is rapidly turned off at the onset of encystation. |
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Keywords: | Entamoeba Encystation Ornithine decarboxylase Polyamine |
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