SialEXO® in a Glycoform Analysis of Intact Erythropoietin

In this study, scientists at Leiden University Medical Center present a MALDI FT-ICR MS method for the glycosylation profiling of intact erythropoietin (EPO). The sialidase mix SialEXO significantly reduced the mass spectrum complexity and facilitated the interpretation of the complex spectra of intact EPO.
 
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Characterization of SARS-CoV-2 Receptor-Binding Domains using SmartEnzymes™

Scientists at Leiden University Medical Center (LUMC) present a multilevel mass spectrometry approach using SmartEnzymes for in-depth characterization of mammalian SARS-CoV-2 receptor-binding (RBD) domains.

The COVID-19 disease caused by the SARS-CoV-2 virus has affected more that 100 million individuals in the ongoing pandemic. The enveloped RNA corona virus contains three structural proteins in the membrane, including the heavily glycosylated spike protein carrying 22 N-glycosylation sites. The spike protein in turn consists of two subunits, S1 and S2, where the receptor-binding domain (RBD) of S1 directly interacts with the ACE2 receptor in the human respiratory tract and facilitates host cell entry. Considering the relevance of RBD glycosylation on ACE2 binding and recognition by neutralizing antibodies, the use of well-characterized S proteins is essential for continued research and development of diagnostic tools and vaccines.

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SmartEnzymes in Targeted Sequencing of Heavily Glycosylated IgA1

The use of IgG-based antibodies in various clinical fields have increased over that past decades, continuing the development of better biopharmaceuticals. The use of other immunoglobulins including IgA, characterized with the ability to recruit effector cells, is progressively being considered a useful alternative. The complexity of the heavily glycosylated IgA does however pose analytical challenges and no method currently exist that allows unraveling of the human repertoire of this subclass.

Scientists at Utrecht University present a mass spectrometry method using electron capture dissociation (EDC) to obtain sequence ladders of the variable regions on the heavily N- and O-glycosylated anti-CD20 IgA1 antibody. Using SmartEnzymes and a native top-down approach, the scientists compared the IgA1 antibody to its anti-CD20 IgG counterpart, and their Fabs.

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FabRICATOR, SialEXO and OglyZOR in Middle-up HILIC/HRMS Approach

In an article by Valentina D’Atri et al. recently published in Analytical Chemistry (2019), the scientists developed a middle-up HILIC/HRMS workflow for detailed characterisation of the Fc fusion protein etanercept.  The etanercept molecule consists of an IgG1 Fc domain fused to a tumour necrosis factor receptor (TNFR) and is used in the treatment of autoimmune diseases such as rheumatoid arthritis. The protein is highly glycosylated and contains numerous O- and N-glycosylation sites that require extensive characterization.

To develop a strategy that would work with a mass spec instrument of limited resolution, the authors used FabRICATOR enzyme to specifically digest the etanercept molecule and generate TNFR and Fc/2 subunits. Combinations of the O- and N- glycosidases SialEXO, OglyZOR and PNGaseF were applied to allow evaluation of the O- and N-glycosylation patterns of TNFR and Fc/2 respectively. In addition, complete deglycosylation allowed for primary structure analysis. By using a wide-pore HILIC stationary phase, appropriate separation of the subunits with different degrees of remaining glycans was achieved, and this significantly facilitated spectra deconvolution.

Applying this workflow, D’Atri and colleagues were able to assess the main PTMs, the subunit distribution of glycans, the overall N/O glycan composition and the sialylation profiles of each subunit.

Read more about the SmartEnzymes in this publication

• FabRICATOR – Enabling middle level analytics
• OglyZOR – Efficient removal of O-glycans
• SialEXO – Getting rid of sialic acids 

Reference:

D’Atri, V. et al., 2018. Orthogonal Middle-up Approaches for Characterization of the Glycan Heterogeneity of Etanercept by Hydrophilic Interaction Chromatography Coupled to High-Resolution Mass Spectrometry. Analytical Chemistry, 91(1), pp.873–880.