Yoram Tekoah

Protalix Biotherapeutics, Tell Afif, Tel Aviv, Israel

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Publications (14)51.04 Total impact

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    ABSTRACT: Fabry disease is an X-linked recessive disorder caused by the loss of function of the lysosomal enzyme α-Galactosidase-A. Although two enzyme replacement therapies (ERTs) are commercially available, they may not effectively reverse some of the Fabry pathology. PRX-102 is a novel enzyme for the therapy of Fabry disease expressed in a BY2 Tobacco cell culture. PRX-102 is chemically modified, resulting in a cross-linked homo-dimer. We have characterized the in-vitro and in-vivo properties of PRX-102 and compared the results with the two commercially produced α-Galactosidase-A enzymes. Results show that PRX-102 has prolonged in-vitro stability in plasma, after 1h incubation it retains 30% activity compared with complete inactivation of the commercial enzymes. Under lysosomal-like conditions PRX-102 maintains over 80% activity following 10days of incubation, while commercial enzymes become inactive after 2days. Pharmacokinetic profile of PRX-102 measured in male Fabry mice shows a 10 fold increase in t1/2 in mice (581min) compared to approved drugs. The enzyme has significantly different kinetic parameters to the alternative ERTs available (p-value<0.05, one way ANOVA), although these differences do not indicate any significant biochemical variations. PRX-102 is uptaken to primary human Fabry fibroblasts. The repeat administration of the enzyme to Fabry mice caused significant reduction (p-value<0.05) of Gb3 in various tissues (the measured residual content was 64% in kidney, liver was cleaned, 23% in heart, 5.7% in skin and 16.2% in spleen). PRX-102 has a relatively simple glycosylation pattern, characteristic to plants, having mainly tri-mannose structures with the addition of either α(1-3)-linked fucose or β(1-2)-linked xylose, or both, in addition to various high mannose structures, while agalsidase beta has a mixture of sialylated glycans in addition to high mannose structures. This study concludes that PRX-102 is equivalent in functionality to the current ERTs available, with superior stability and prolonged circulatory half-life. Therefore we propose that PRX-102 is a promising alternative for treatment of Fabry disease.
    Molecular Genetics and Metabolism 08/2014; · 2.83 Impact Factor
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    ABSTRACT: N-glycosylation is one of the most important post-translational modifications that influence protein polymorphism, including protein structures and their functions. Although this important biological process has been extensively studied in mammals, only limited knowledge exists regarding glycosylation in algae. The current research is focused on the red microalga Porphyridium sp., which is a potentially valuable source for various applications, such as skin therapy, food, and pharmaceuticals. The enzymes involved in the biosynthesis and processing of N-glycans remain undefined in this species, and the mechanism(s) of their genetic regulation is completely unknown. In this study, we describe our pioneering attempt to understand the endoplasmic reticulum N-Glycosylation pathway in Porphyridium sp., using a bioinformatic approach. Homology searches, based on sequence similarities with genes encoding proteins involved in the ER N-glycosylation pathway (including their conserved parts) were conducted using the TBLASTN function on the algae DNA scaffold contigs database. This approach led to the identification of 24 encoded-genes implicated with the ER N-glycosylation pathway in Porphyridium sp. Homologs were found for almost all known N-glycosylation protein sequences in the ER pathway of Porphyridium sp.; thus, suggesting that the ER-pathway is conserved; as it is in other organisms (animals, plants, yeasts, etc.).
    International Journal of Molecular Sciences 01/2014; 15(2):2305-26. · 2.46 Impact Factor
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    ABSTRACT: The glycosylation of recombinant β-glucocerebrosidase, and in particular the exposure of mannose residues, has been shown to be a key factor in the success of enzyme replacement therapy (ERT) for the treatment of Gaucher disease. Macrophages, the target cells in Gaucher disease, internalize β-glucocerebrosidase through mannose receptors. Three enzymes are commercially available for the treatment of Gaucher disease by ERT. Taliglucerase alfa, imiglucerase, and velaglucerase alfa are each produced in different cell systems and undergo various post-translational or post-production glycosylation modifications to expose their mannose residues. This is the first study in which the glycosylation profiles of the three enzymes are compared, using the same methodology and the effect on functionality and cellular uptake is evaluated. While the major differences in glycosylation profiles reside in the variation of terminal residues and mannose chain length, the enzymatic activity and stability are not affected by these differences. Furthermore, the cellular uptake and in-cell stability in rat and human macrophages are similar. Finally, in vivo studies to evaluate the uptake into target organs also show similar results for all three enzymes. These results indicate that the variations of glycosylation between the three regulatory-approved β‑glucocerebrosidase enzymes have no effect on their function or distribution.
    Bioscience Reports 08/2013; · 1.88 Impact Factor
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    ABSTRACT: We report here the structural determination of the N-linked glycans in the 66-kDa glycoprotein, part of the unique sulfated complex cell wall polysaccharide of the red microalga Porphyridium sp. Structures were elucidated by a combination of normal phase/reverse phase HPLC, positive ion MALDI-TOF MS, negative ion electrospray ionization, and MS/MS. The sugar moieties of the glycoprotein consisted of at least four fractions of N-linked glycans, each composed of the same four monosaccharides, GlcNAc, Man, 6-O-MeMan, and Xyl, with compositions Man(8-9)Xyl(1-2)Me(3)GlcNAc(2). The present study is the first report of N-glycans with the terminal Xyl attached to the 6-mannose branch of the 6-antenna and to the 3-oxygen of the penultimate (core) GlcNAc. Another novel finding was that all four glycans contain three O-methylmannose residues in positions that have never been reported before. Although it is known that some lower organisms are able to methylate terminal monosaccharides in glycans, the present study on Porphyridium sp. is the first describing an organism that is able to methylate non-terminal mannose residues. This study will thus contribute to understanding of N-glycosylation in algae and might shed light on the evolutionary development from prokaryotes to multicellular organisms. It also may contribute to our understanding of the red algae polysaccharide formation. The additional importance of this research lies in its potential for biotechnological applications, especially in evaluating the use of microalgae as cell factories for the production of therapeutic proteins.
    Journal of Biological Chemistry 06/2011; 286(24):21340-52. · 4.65 Impact Factor
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    ABSTRACT: Finding new peptide biomarkers for stomach cancer in human sera that can be implemented into a clinically practicable prediction method for monitoring of stomach cancer. We studied the serum peptidome from two different biorepositories. We first employed a C8-reverse phase liquid chromatography approach for sample purification, followed by mass-spectrometry analysis. These were applied onto serum samples from cancer-free controls and stomach cancer patients at various clinical stages. We then created a bioinformatics analysis pipeline and identified peptide signature discriminating stomach adenocarcinoma patients from cancer-free controls. Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) results from 103 samples revealed 9 signature peptides; with prediction accuracy of 89% in the training set and 88% in the validation set. Three of the discriminating peptides discovered were fragments of Apolipoproteins C-I and C-III (apoC-I and C-III); we further quantified their serum levels, as well as CA19-9 and CRP, employing quantitative commercial-clinical assays in 142 samples. ApoC-I and apoC-III quantitative results correlated with the MS results. We then employed apoB-100-normalized apoC-I and apoC-III, CA19-9 and CRP levels to generate rules set for stomach cancer prediction. For training, we used sera from one repository, and for validation, we used sera from the second repository. Prediction accuracies of 88.4% and 74.4% were obtained in the training and validation sets, respectively. Serum levels of apoC-I and apoC-III combined with other clinical parameters can serve as a basis for the formulation of a diagnostic score for stomach cancer patients.
    PLoS ONE 01/2011; 6(1):e14540. · 3.53 Impact Factor
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    ABSTRACT: Streptococcus iniae is a major pathogen of fish, causing considerable economic losses in Israel, the United States and the Far East. Containment of mortalities through vaccination was recently compromised due to the emergence of novel vaccine-escape strains that are distinguished from previous strains by their ability to produce large amounts of extracellular polysaccharide (EPS) that is released to the medium. In vitro and in vivo data now indicate that the EPS is a major virulence factor, capable of triggering the proinflammatory cytokine machinery and inducing mortality of fish. Streptococcus iniae EPS might therefore be considered to be responsible for sepsis and death just as lipopolysaccharide is for Gram-negative pathogens.
    FEMS Microbiology Letters 02/2010; 305(2):109-20. · 2.05 Impact Factor
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    ABSTRACT: Natural killer (NK) cells serve as a crucial first-line defense against tumors and virus-infected cells. We previously showed that lysis of influenza virus (IV)-infected cells is mediated by the interaction between the NK receptor, NKp46, and the IV hemagglutinin (HA) type 1 expressed by the infected cells. This interaction requires the presence of sialyl groups on the NKp46-T225 O-glycoforms. In the current study, we analyzed the O-glycan sequences that are imperative for the interaction between recombinant NKp46 (rNKp46) and IV H1N1 strains. We first showed that rNKp46 binding to IV H1N1 is not mediated by a glycoform unique to the Thr225 site. We then characterized the O-glycan sequences that mediate the interaction of rNKp46 and IV H1N1; we employed rNKp46s with dissimilar glycosylation patterns and IV H1N1 strains with different sialic acid alpha2,3 and alpha2,6 linkage preferences. The branched alpha2,3-sialylated O-glycoform Neu5NAcalpha2,3-Galbeta1,4-GlcNAcbeta1,6[Neu5NAcalpha2,3-Galbeta1,3]GalNAc competently mediated the interaction of rNKp46 with IV H1N1, manifesting a preference for alpha2,3 linkage. In contrast, the linear alpha2,3-sialylated O-glycoform Neu5NAcalpha2,3-Galbeta1,3-GalNAc was not correlated with enhanced interaction between rNKp46 and IV H1N1 or a preference for alpha2,3 linkage. The branched alpha2,3- and alpha2,6-sialylated O-glycoform Neu5NAcalpha2,3-Galbeta1,3[Neu5NAcalpha2,6]GalNAc competently mediated the interaction of rNKp46 with IV H1N1, manifesting a preference for alpha2,6 linkage. Previous viral HA-binding-specificity studies were performed with glycopolymer conjugates, free synthetic sialyl oligosaccharides, and sialidase-treated cells. This study shed light on the O-glycan sequences involved in the interaction of glycoprotein and viral hemagglutinins and may help in the design of agents inhibitory to hemagglutinin for influenza treatment.
    Journal of Virology 02/2010; 84(8):3789-97. · 5.08 Impact Factor
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    ABSTRACT: Mushroom polysaccharides are potent substances that exhibit antitumor and immunomodulatory properties. Studies comparing the chemical composition and antitumor-related activities of polysaccharides released by fungal strains under different growth conditions are not available. Thus, the present study compared polysaccharides extracts produced by Pleurotus pulmonarius from mycelium grown in liquid culture (ME) or fruiting bodies (FBE). Polysaccharides of both ME and FBE had a relatively high molecular mass. NMR spectroscopy indicated that ME glucan is an alpha-glucan whereas FBE glucan is a mixture of both alpha- and beta-glucans. Glucose and galactose where the most prominent monosaccharide in both glucans. Treatment of several colon cancer cell lines expressing varying amounts of galectin-3 with the two fungal glucans inhibited their viability and significantly reduced their ability to adhere to the key component of the extracellular matrix, fibronectin, and to a human umbilical vein endothelial cell monolayer, in a time- and dose-dependent manner mainly in those cell lines expressing high amounts of galectin-3. We conclude that ME and FBE glucans may exert a direct antiproliferative effect on cancer cells expressing high galectin-3 concentrations and concomitantly downregulate tumor cell adherence, the latter being directly related to cancer progression and metastasis.
    Applied Microbiology and Biotechnology 10/2009; 85(6):1977-90. · 3.69 Impact Factor
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    ABSTRACT: The current study forms part of an ongoing research effort focusing on the elucidation of the chemical structure of the sulfated extracellular polysaccharide of the red microalga Porphyridium sp. (UTEX 637). We report here on the chemical structure of a fraction separated from an acidic crude extract of the polysaccharide, as investigated by methylation analysis, carboxyl reduction-methylation analysis, desulfation-methylation analysis, partial acid hydrolysis, Smith degradation, together with 1D and 2D (1)H and (13)C NMR spectroscopy. This fraction with a molar mass of 2.39x10(5)g mol(-1) comprised D- and L-Gal, D-Glc, D-Xyl, D-GlcA, and sulfate groups in a molar ratio of 1.0:1.1:2.1:0.2:0.7. The almost linear backbone of the fraction is composed of (1-->2)- or (1-->4)-linked d-xylopyranosyl, (1-->3)-linked L-galactopyranosyl, (1-->3)-linked D-glucopyranosyl, and (1-->3)-linked D-glucopyranosyluronic acid and comprises a possible acidic building unit: [(2 or 4)-beta-D-Xylp-(L-->3)]m-alpha-D-Glcp-(1-->3)-alpha-D-GLCPA-(1-->3)-L-Galp(l-->. Attached to the backbone are sulfate groups and nonreducing terminal D-xylopyranosyl and galactopyranosyl residues, which occur at the O-6 positions of Glc-derived moieties in the main chain.
    Carbohydrate research 01/2009; 344(3):343-9. · 2.03 Impact Factor
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    ABSTRACT: Streptococcus iniae is a major pathogen of fish, producing fatal disease among fish species living in very diverse environments. Recently, reoccurrences of disease outbreaks were recorded in rainbow trout (Oncorhynchus mykiss, Walbaum) farms where the entire fish population was routinely vaccinated. New strains are distinguished from previous strains by their ability to produce large amounts of extracellular polysaccharide that is released into the medium. Present findings indicate that the extracellular polysaccharide is a major antigenic factor, suggesting an evolutionary selection of strains capable of extracellular polysaccharide production.
    Applied and Environmental Microbiology 10/2008; 74(22):6892-7. · 3.95 Impact Factor
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    ABSTRACT: We hypothesized that biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)--a widely used explosive contaminating soil and groundwater--by Rhodococcus strain YH1 is controlled by the presence of external nitrogen sources. This strain is capable of degrading RDX while using it as sole nitrogen source under aerobic conditions. Both inorganic and organic nitrogen sources were found to have a profound impact on RDX-biodegradation activity. This effect was tested in growing and resting cells of strain YH1. Nitrate and nitrite delayed the onset of RDX degradation by strain YH1, while ammonium inhibited it almost completely. In addition, 2,4,6-trinitrotoluene (TNT) inhibited RDX degradation and growth of strain YH1. On the other hand, tetrahydrophthalamide did not influence biodegradation or growth. Growth on RDX induced the expression of a cytochrome P-450 enzyme that is suggested to be involved in the first step in the aerobic pathway of RDX degradation, as identified by SDS-PAGE analysis. Ammonium and nitrite strongly repressed cytochrome P-450 expression. Our findings suggest that effective RDX bioremediation by strain YH1 requires the design of a treatment scheme that includes initial removal of ammonium, nitrite, nitrate and TNT before RDX degradation can take place.
    Biodegradation 07/2008; 19(3):313-20. · 2.17 Impact Factor
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    ABSTRACT: NKp30 is a natural cytotoxicity receptor expressed by human NK cells and involved in NK lytic activity. We previously published that membranal heparan sulfate serves as a coligand for human NKp30. In the present study, we complement our results by showing direct binding of recombinant NKp30 to immobilized heparin. The heparan sulfate epitope(s) on target tumor cells and the heparin epitope(s) recognized by NKp30 share similar characteristics. Warren and colleagues (Warren HS, Jones AL, Freeman C, Bettadapura J, Parish CR. 2005. Evidence that the cellular ligand for the human NK cell activation receptor NKp30 is not a heparan sulfate glycosaminoglycan. J Immunol. 175:207-212) published that NKp30 does not bind to membranal heparan sulfate on target cells and that heparan sulfate is not involved in NKp30-mediated lysis. In the current study, we examine the binding of six different recombinant NKp30s to membranal heparan sulfate and conclude that NKp30 does interact with membranal heparan sulfate. Yet, two of the six recombinant NKp30s, including the commercially available recombinant NKp30 (employed by Warren et al.) did not show heparan sulfate-dependent binding. We demonstrate that this is due to an altered glycosylation of these two recombinant NKp30s. Upon removal of its N-linked glycans, heparan sulfate-dependent binding to tumor cells and direct binding to heparin were restored. Overall, our results emphasize the importance of proper glycosylation for analysis of NKp30 binding to its ligand and that membranal heparan sulfate could serve as a coligand for NKp30. At the cellular level, soluble heparan sulfate enhanced the secretion of IFNgamma by NK-92 natural killer cells activated with anti-NKp30 monoclonal antibody. We discuss the involvement of heparan sulfate binding to NKp30 in NKp30-mediated activation of NK cells.
    Glycobiology 02/2008; 18(1):28-41. · 3.54 Impact Factor
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    ABSTRACT: Recombinant therapeutic monoclonal antibodies (mAb) can be expressed, assembled, and glycosylated in plants. Transgenic plants, producing anti-rabies mAb and anti-colorectal cancer mAb, were obtained from Agrobacterium-mediated transformation. The heavy chain (HC) of anti-rabies mAb was fused to the Lys-Asp-Glu-Leu (KDEL) endoplasmic reticulum retention signal whereas the HC of anti-colorectal cancer mAb was not fused to the KDEL sequence. Gel release of glycans and detection by high-performance liquid chromatography (HPLC), together with computer assisted analysis and matrix-assisted laser desorption/ionization time-of-flight (MALD-TOF) mass spectrometry, revealed that the plant-derived anti-rabies mAb with KDEL contained mainly oligomannose type N-glycans while the plant-derived anti-colorectal cancer mAb carried mainly biantennary glycans with and without a pentose sugar, that is thought to be xylose. This finding indicates that the KDEL sequence can affect the N-glycosylation processing of antibody in plant cells. The plant-derived mAbs with addition of a KDEL sequence did not contain any of the known antigenic glycan epitopes that are frequently found in other plant glycans or in mammalian-derived mAbs. The altered glycosylation on both plant-derived mAbs did not affect the activities that are required for therapy. These results indicate that plant genetic engineering could provide an effective and inexpensive means to control the glycosylation of therapeutic proteins such as mAbs, by the addition of a KDEL signal as a regulatory element.
    Archives of Biochemistry and Biophysics 07/2004; 426(2):266-78. · 3.37 Impact Factor
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    ABSTRACT: Plant genetic engineering led to the production of plant-derived mAb (mAbP), which provides a safe and economically feasible alternative to the current methods of antibody production in animal systems. In this study, the heavy and light chains of human anti-rabies mAb were expressed and assembled in planta under the control of two strong constitutive promoters. An alfalfa mosaic virus untranslated leader sequence and Lys-Asp-Glu-Leu (KDEL) endoplasmic reticulum retention signal were linked at the N and C terminus of the heavy chain, respectively. mAbP was as effective at neutralizing the activity of the rabies virus as the mammalian-derived antibody (mAbM) or human rabies Ig (HRIG). The mAbP contained mainly oligomannose type N-glycans (90%) and had no potentially antigenic alpha(1,3)-linked fucose residues. mAbP had a shorter half-life than mAbM. The mAbP was as efficient as HRIG for post-exposure prophylaxis against rabies virus in hamsters, indicating that differences in N-glycosylation do not affect the efficacy of the antibody in this model.
    Proceedings of the National Academy of Sciences 07/2003; 100(13):8013-8. · 9.81 Impact Factor

Publication Stats

256 Citations
51.04 Total Impact Points


  • 2014
    • Protalix Biotherapeutics
      Tell Afif, Tel Aviv, Israel
  • 2008–2011
    • Ben-Gurion University of the Negev
      • • Shraga Segal Department of Microbiology and Immunology
      • • Faculty of Health Sciences
      Beersheba, Southern District, Israel
  • 2003–2004
    • University of Oxford
      • Department of Biochemistry
      Oxford, ENG, United Kingdom