Three new G6PD variants, G6PD Adana, G6PD Samanda?, and G6PD Balcali in �ukurova, Turkey

Aksoy, Kıymet; Yüreğir, Guneş T.; Dikmen, Nurten; Unlukurt, Isa

doi:10.1007/bf00284922

Cited by 5 publications

(1 citation statement)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Interestingly, Blastocystis legumain has biphasic pH dependence, with peaks at pH 4.0 and 7.5, a property that has not been seen in legumains from all other origins, and is infrequently observed among enzymes in general. Some individuals with glucose-6-phosphate dehydrogenase deficiency harbor variant glucose-6-phosphate dehydrogenases that display biphasic pH optimum curves (28,29). In a study on renin pH dependence, it was shown that Ser-84 of human renin contributes to the biphasic pH dependence of the renin-angiotensinogen reaction (30).…”

Section: Discussionmentioning

confidence: 99%

Blastocystis Legumain Is Localized on the Cell Surface, and Specific Inhibition of Its Activity Implicates a Pro-survival Role for the Enzyme

Yin

Texier

et al. 2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

Programmed cell death (PCD) is crucial for cellular growth and development in multicellular organisms. Although distinct PCD features have been described for unicellular eukaryotes, homology searches have failed to reveal clear PCD-related orthologues among these organisms. Our previous studies revealed that a surface-reactive monoclonal antibody (mAb) 1D5 could induce multiple PCD pathways in the protozoan Blastocystis. In this study, we identified, by two-dimensional gel electrophoresis and mass spectrometry, the target of mAb 1D5 as a surface-localized legumain, an asparagine endopeptidase that is usually found in lysosomal/acidic compartments of other organisms. Recombinant Blastocystis legumain displayed biphasic pH optima in substrate assays, with peaks at pH 4 and 7.5. Activity of Blastocystis legumain was greatly inhibited by the legumain-specific inhibitor carbobenzyloxy-Ala-Ala-AAsn-epoxycarboxylate ethyl ester (APE-RR) (where AAsn is aza-asparagine) and moderately inhibited by mAb 1D5, cystatin, and caspase-1 inhibitor. Interestingly, inhibition of legumain activity induced PCD in Blastocystis, observed by increased externalization of phosphatidylserine residues and in situ DNA fragmentation. In contrast to plants, in which legumains have been shown to play a pro-death role, legumain appears to display a pro-survival role in Blastocystis.Programmed cell death in the unicellular protozoa is now accepted as a well established phenomenon. Several stereotypic apoptotic morphological markers similar to those observed in apoptotic metazoan cells have been described in human parasitic protozoa such as Leishmania amazonensis, Leishmania donovani, Trypanosoma cruzi, Trypanosoma brucei, Trypanosoma rhodesiense, Plasmodium falciparum, and Blastocystis (1, 2). Despite a wealth of information on the organelles and cytochemical features involved in protozoan PCD, there is a scarcity of information on PCD 3 -related molecular mediators. Our earlier studies showed that Blastocystis undergoes programmed cell death when exposed to the surface-reactive monoclonal antibody mAb 1D5 with typical features of apoptotic cells (3, 4). mAb 1D5 was shown to target a 30-kDa protein found on the plasma membrane of Blastocystis (5-7). This protein is functionally important, but not all cells within a clonal population would be susceptible to the cytotoxic effects of mAb 1D5 (6). These results suggest that this protein may have multiple localizations and is potentially important for cell survival. In this study, an asparaginyl cysteine protease legumain was identified as the mAb 1D5 targeting protein. Legumain is a recently described lysosomal protease, well conserved and present in plants, mammals, helminth worms, and the protozoan Trichomonas vaginalis (8 -12). The active site of legumain contains the catalytic dyad His-Gly-spacer-Ala-Cys, a characteristic shared with caspases, aspartyl cysteine proteases important as molecular mediators of apoptosis cascades (13). Legumains have specificity for the hydrolysis of bonds on the carb...

show abstract

Section: Discussionmentioning

confidence: 99%