Bravo-Torres JC, Villagómez-Castro JC, Calvo-Méndez C, Flores-Carreón A, López-Romero E. Purification and biochemical characterisation of a membrane-bound α-glucosidase from the parasite Entamoeba histolytica.
Int J Parasitol 2004;
34:455-62. [PMID:
15013735 DOI:
10.1016/j.ijpara.2003.11.015]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2003] [Revised: 10/22/2003] [Accepted: 11/05/2003] [Indexed: 10/26/2022]
Abstract
An alpha-glucosidase was solubilised from a mixed membrane fraction of Entamoeba histolytica and purified to homogeneity by a two-step procedure consisting of ion exchange chromatography in a Mono Q column and affinity chromatography in concanavalin A-sepharose. Although the enzyme failed to bind the lectin, this step rendered a homogenous and more stable enzyme preparation that resolved into a single polypeptide of 55 kDa after SDS-PAGE. As measured with 4-methylumbelliferyl-alpha-D-glucopyranoside (MUalphaGlc) as substrate, glycosidase activity was optimum at pH 6.5 with different buffers and at 45 degrees C. Although the enzyme preferentially hydrolysed nigerose (alpha1,3-linked), it also cleaved kojibiose (alpha1,2-linked), which was the second preferred substrate, and to a lesser extent maltose (alpha1,4), trehalose (alpha1,1) and isomaltose (alpha1,6). Activity on alpha1,3- and alpha1,2-linked disaccharides was strongly inhibited by the glycoprotein processing inhibitors 1-deoxynojirimycin and castanospermine but was unaffected by australine. Glucose and particularly 3-deoxy-D-glucose and 6-deoxy-D-glucose were strong inhibitors of activity, whereas 2-deoxy-D-glucose and other monosaccharides had no effect. Enzyme activity on MUalphaGlc was very sensitive to inhibition by diethylpyrocarbonate suggesting a critical role of histidine residues in enzyme catalysis. Other amino acid modifying reagents such as N-ethylmaleimide and N-(3-dimethylaminopropyl)-N'ethylcarbodiimide showed a moderate effect or none at all, respectively. Results are discussed in terms of the possible involvement of this glycosidase in N-glycan processing.
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