Temperature-dependent mycotoxins production investigation in Alternaria infected cherry by ultra-high performance liquid chromatography and Orbitrap high resolution mass spectrometry.

For temperature-dependent Alternaria mycotoxins production analysis, cherry samples were inoculated with Alternaria sp. and incubated at two different temperatures (4 °C and 25 °C). Six Alternaria mycotoxins, including altenuene (ALT), alternariol monomethyl ether (AME), alternariol (AOH), altertoxin-I (ATX-I), tenuazonic acid (TeA), and tentoxin (TEN), in cherries were detected with integrated visible data-processing tools. Maximum concentration of these mycotoxins reached 71,862.2 µg/kg at 25 °C. Notably, considerable amount of TeA (290.4 µg/kg) was detected at 4 °C, which indicated that low temperature is not a safe storage condition for fruits. A total of 102 compounds were detected with a neutral loss of 162.0528 Da, and TeA-glucose was identified in this work. Based on MS/MS cosine similarity, products were verified and annotated with feature based molecular networking (FBMN) in global natural products social networking (GNPS). The results showed Alternaria mycotoxins in cherry samples were mainly demethylation, hydrogenation, and dehydration. This work revealed the production of Alternaria mycotoxins in cherries under different storage temperature, which will provide theoretical basis for the control of mycotoxin contamination in food commodities.

[Expression of a SARS-CoV-2 neutralizing nanobody in Trichoderma reesei].

Nanobodies derived from camelid single-chain antibodies have the advantages of being small, simple, highly soluble and stable. Nanobodies can be administered by inhalation and therefore is potentially valuable for the prevention and control of respiratory viruses. Trichoderma reesei is a food-grade protein expression host with a cellulase production capacity of up to 80 g/L, which can be employed for low-cost production of therapeutic proteins. In this study, a codon-optimized SARS-CoV-2 neutralizing nanobody Nb20 was expressed in T. reesei under a strong constitutive promoter Pcdna1. Nb20 protein was fused downstream of the N-terminal fragment of cellobiohydrolase Ⅰ, and the fusion protein can be intracellularly cleaved by the KEX2 protease to release Nb20. In a shake-flask fermentation using glucose medium, 47.4 mg/L Nb20 was detected in the culture after 48 h of cultivation. The expressed Nb20 showed the ability to interact with the receptor-binding domain of SARS-CoV-2 spike protein, suggesting that it can be used for the neutralization of SARS-CoV-2. The results indicate that T. reesei has the potential for recombinant production of nanobodies.

Streamlined Subclass-Specific Absolute Quantification of Serum IgG Glycopeptides Using Synthetic Isotope-Labeled Standards.

Absolute glycoproteomics quantification has drawn tremendous attention owing to its prospects in biomarker discovery and clinical implementation but is impeded by a general lack of suitable heavy isotope-labeled glycopeptide standards. In this study, we devised a facile chemoenzymatic strategy to synthesize a total of 36 human IgG glycopeptides attached with well-defined glycoforms, including 15 isotope-labeled ones with a mass increment of 6 Da to their native counterparts. Spiking of these standards into human sera enabled simplified, robust, and precise absolute quantification of IgG glycopeptides in a subclass-specific fashion. Additionally, the implementation of the absolute quantification approach revealed subclass-dependent alteration of serum IgG galactosylation and sialylation in colon cancer samples.

Penicillium oxalicum putative methyltransferase Mtr23B has similarities and differences with LaeA in regulating conidium development and glycoside hydrolase gene expression.

Putative methyltranferase LaeA and LaeA-like proteins, which are conserved in many filamentous fungi, regulate the sporogenesis and biosynthesis of secondary metabolites. In this study, we reported the biological function of a LaeA-like methyltransferase, Penicillium oxalicum Mtr23B, which contains a methyltransf_23 domain and an S-adenosylmethionine binding domain, in controlling spore pigment formation and in the expression of secondary metabolic gene cluster and glycoside hydrolase genes. Additionally, we compared Mtr23B and LaeA, and determined their similarities and differences in terms of their roles in regulating the above biological processes. mtr23B had the highest transcriptional level among the 12 members of the methyltransf_23 family in P. oxalicum. The colony color of Δmtr23B (deletion of mtr23B) was lighter than that of ΔlaeA, although Δmtr23B produced ~ 19.2-fold more conidia than ΔlaeA. The transcriptional levels of abrA, abrB/yA, albA/wA, arpA, arpB, and aygA, which are involved in the dihydroxynaphtalene-melanin pathway, decreased in Δmtr23B. However, Mtr23B had a little effect on brush-like structures and conidium formation, and had a different function from LaeA. Mtr23B extensively regulated glycoside hydrolase gene expression. The absence of Mtr23B remarkably repressed prominent cellulase- and amylase-encoding genes in the whole culture period, while the effect of LaeA mainly occurred in the later phases of prolonged batch cultures. Similar to LaeA, Mtr23B was involved in the expression of 10 physically linked regions containing secondary metabolic gene clusters; the highest regulatory activities of Mtr23B and LaeA were observed in BrlA-dependent cascades. Although LaeA interacted with VeA, Mtr23B did not interact with VeA directly. We assumed that Mtr23B regulates cellulase and amylase gene transcription by interacting with the CCAAT-binding transcription factor HAP5 and chromatin remodeling complex.

Comparative glycosylation mapping of plasma-derived and recombinant human factor VIII.

Human coagulation factor VIII (FVIII) is a key co-factor in the clotting cascade, the deficiency of which leads to Hemophilia A. Human plasma-derived (pdFVIII) and recombinant FVIII (rFVIII) had been used as effective products to prevent and treat bleeding episodes. Both FVIII products share identical amino acid sequences and appear to be equivalent as of clinical efficiency. However, systemic reviews found an increased risk of neutralizing antibody (or inhibitor) development with recombinant products. FVIII is a highly glycosylated protein, and its glycosylation pattern is specific to host cells and environments. The roles of glycosylation in immune responses toward pdFVIII and rFVIII are yet to be defined. Herein, we systemically profiled N- and O-glycomes of pdFVIII and rFVIII using a mass spectrometry-based glycoproteomic strategy. A total of 110 site-specific N-glycopeptides consisting of 61 N-glycoforms were identified quantitatively from rFVIII and pdFVIII. Additionally, 31 O-glycoforms were identified on 23 peptides from rFVIII and pdFVIII. A comprehensive comparison of their site-specific glycan profiles revealed distinct differences between the glycosylation of pdFVIII and rFVIII.

Enzymatic rhamnosylation of anticancer drugs by an α-L-rhamnosidase from Alternaria sp. L1 for cancer-targeting and enzyme-activated prodrug therapy.

The synthesis of rhamnosylated compounds has gained great importance since these compounds have potential therapeutic applications. The enzymatic approaches for glycosylation of bioactive molecules have been well developed; however, the enzymatic rhamnosylation has been largely hindered by lacking of the glycosyl donor for rhamnosyltransferases. Here, we employed an α-L-rhamnosidase from Alternaria sp. L1 (RhaL1) to perform one-step rhamnosylation of anticancer drugs, including 2'-deoxy-5-fluorouridine (FUDR), cytosine arabinoside (Ara C), and hydroxyurea (Hydrea). The key synthesis conditions including substrate concentrations and reaction time were carefully optimized, and the maximum yields of each rhamnosylated drugs were 57.7 mmol for rhamnosylated Ara C, 68.6 mmol for rhamnosylated Hydrea, and 42.2 mmol for rhamnosylated FUDR. It is worth pointing out that these rhamnosylated drugs exhibit little cytotoxic effects on cancer cells, but could efficiently restore cytotoxic activity when incubated with exogenous α-L-rhamnosidase, suggesting their potential applications in the enzyme-activated prodrug system. To evaluate the cancer-targeting ability of rhamnose moiety, the rhamnose-conjugated fluorescence dye rhodamine B (Rha-RhB) was constructed. The fluorescence probe Rha-RhB displayed much higher cell affinity and cellular internalization rate of oral cancer cell KB and breast cancer cell MDA-MB-231 than that of the normal epithelial cells MCF 10A, suggesting that the rhamnose moiety could mediate the specific internalization of rhamnosylated compounds into cancer cells, which greatly facilitated their applications for cancer-targeting drug delivery.

Three glycoside hydrolase family 12 enzymes display diversity in substrate specificities and synergistic action between each other.

PoCel12A, PoCel12B, and PoCel12C are genes that encode glycoside hydrolase family 12 (GH12) enzymes in Penicillium oxalicum. PoCel12A and PoCel12B are typical GH12 enzymes that belong to fungal subfamilies 12-1 and 12-2, respectively. PoCel12C contains a low-complexity region (LCR) domain, which is not found in PoCel12A or PoCel12B and independent of fungal subfamily 12-1 or 12-2. Recombinant enzymes (named rCel12A, rCel12B and rCel12C) demonstrate existing diversity in the substrate specificities. Although most members in GH family 12 are typical endoglucanases and preferentially hydrolyze ß-1,4-glucan (e.g., carboxymethylcellulose), recombinant PoCel12A is a non-typical endo-(1-4)-ß-glucanase; it preferentially hydrolyzes mix-linked ß-glucan (barley ß-glucan, ß-1,3-1,4-glucan) and slightly hydrolyzes ß-1,4-glucan (carboxymethylcellulose). Recombinant PoCel12B possesses a significantly high activity against xyloglucan. A specific activity of rCel12B toward xyloglucan (239 µmol/min/mg) is the second-highest value known. Recombinant PoCel12C shows low activity toward ß-glucan, carboxymethylcellulose, or xyloglucan. All three enzymes can degrade phosphoric acid-swollen cellulose (PASC). However, the hydrolysis products toward PASC by enzymes are different: the main hydrolysis products are cellotriose, cellotetraose, and cellobiose for rCel12A, rCel12B, and rCel12C, correspondingly. A synergistic action toward PASC among rCel12A and rCel12B is observed, thereby suggesting a potential application for preparing enzyme cocktails used in lignocellulose hydrolysis.

Glucose oxidase and polydopamine functionalized iron oxide nanoparticles: combination of the photothermal effect and reactive oxygen species generation for dual-modality selective cancer therapy.

Cancer cells possess some inherent characteristics, such as glucose-dependence and intolerance to heat and exogenous reactive oxygen species (ROS). In this study, a strategy has been developed to target these vulnerable weaknesses of cancer cells using glucose oxidase (GOx) and polydopamine (PDA) functionalized iron oxide nanoparticles (Fe3O4@PDA/GOx NPs). PDA is first deposited on the surfaces of iron oxide NPs through self-polymerization, and then GOx is covalently linked with PDA upon mixing the enzyme and Fe3O4@PDA under alkaline conditions. In this system, the PDA layer along with iron oxide NPs serves as a photothermal transfer material converting near infrared (NIR) radiation into heat. The covalently linked GOx can competitively consume glucose and spontaneously generate ROS H2O2 that can be further converted by the iron oxide NPs into more toxic ˙OH, inducing apoptosis of cancer cells. The selective toxicity of Fe3O4@PDA/GOx NPs on cancer cells is demonstrated both in vitro and in vivo. In particular, a single injection rather than multiple doses results in significant suppression of tumors, and does not induce apparent histological lesions in the 4T1 tumor-bearing Balb/c mice. The versatility of the functionalization strategy reported in this study will contribute to developing efficient therapies for selective cancer treatment.

Identification of Key Components for the Optimization of Cellulase Mixtures Using a Proteomic Strategy.

Efficient degradation of complex lignocellulosic materials requires the synergistic action of different types of enzymes. Characterizing the compositions of lignocellulolytic enzyme mixtures could provide comprehensive understandings about the enzymatic degradation of lignocelluloses. In this chapter, we present a proteomic strategy for the analysis of enzyme mixtures produced by lignocellulolytic fungi. The described method is easy to carry out and is suitable to determine the composition of lignocellulolytic enzyme mixtures in a semiquantitative manner. Comparison of the compositions of enzyme mixtures with different degrading efficiencies allows for the identification of candidate targets for the optimization of lignocellulolytic enzyme mixtures.

Rational designed mutagenesis of levansucrase from Bacillus licheniformis 8-37-0-1 for product specificity study.

Levansucrases, which belong to the glycoside hydrolase family 68 (GH68), synthesize ß (2-6)-linked fructan levan with sucrose as substrate. We described the use of a levansucrase (Bl_SacB) from Bacillus licheniformis 8-37-0-1 for catalysis of fructosyl transfer to obtain high levan yield previously. In the present study, six variants (Y246A, N251A, K372A, R369A, R369S, and R369K) were constructed through sequence alignment and structural analysis to explore the synthesis mechanism of Bl_SacB. The selected residues were predicted to localize to the substrate-entering channel of the active cavity and close to or remote from the catalytic triad. The products of these variants ranged from homopolymers levan to fructo-oligosaccharides (FOSs). The primary FOSs were identified through MS and NMR analyses as neolevan-type neokestose [ß-D-Fru-(2-6)-α-D-Glc-(1-2)-ß-D-Fru], levan-type 6-kestose [ß-D-Fru-(2-6)-ß-D-Fru-(2-1)-α-D-Glc], and inulin-type 1-kestose [ß-D-Fru-(2-1)-ß-D-Fru-(2-1)-α-D-Glc]. The mutation at Tyr246 located remote from the catalytic triad led to the production of short-chain oligosaccharides with degree of polymerization (DP) of up to 25. The replaced Arg369 located close to the catalytic triad resulted in either elimination of polysaccharide synthesis or complete change in the dominant linkage of the products. The Michaelis constants (Km) of Y246A, N251A, K372A, and R369K were found to be similar to that of the wild type (WT). However, the turnover number (kcat) and the value of transfructosylation versus hydrolysis activity of the six variants decreased compared with those of the WT. Hence, the residues located on the surface of the substrate-entering channel of Bl_SacB can be critical in product linkage type and/or elongation mechanism.

A general strategy for the synthesis of homogeneous hyaluronan conjugates and their biological applications.

Here, we developed a general strategy for synthesizing homogeneous HA conjugates, and generated homogeneous HA-pNP, HA-biotin, and HA-oroxylin conjugates to investigate the relationships between HA chain length and its diverse biological functions.

Diethylaminoethyl Sepharose (DEAE-Sepharose) microcolumn for enrichment of glycopeptides.

N-Glycosylation is one of the most prevalent protein post-translational modifications and is involved in many biological processes, such as protein folding, cellular communications, and signaling. Alteration of N-glycosylation is closely related to the pathogenesis of diseases. Thus, the investigation of protein N-glycosylation is crucial for the diagnosis and treatment of disease. In this research, we applied diethylaminoethanol (DEAE) Sepharose solid-phase extraction microcolumns for N-glycopeptide enrichment. This method integrated the advantages of Click Maltose and zwitterionic HILIC (ZIC-HILIC) and showed a relatively higher specificity for N-glycosylated peptides. This strategy was then applied to tryptic digests of normal human serum, followed by deglycosylation using peptide-N-glycosidase F (PNGase F) in H218O. Subsequent LC-MS/MS analysis allowed for the assignment of 219 N-glycosylation sites from 115 serum N-glycoproteins. This study provides an alternative approach for N-glycopeptide enrichment and the method employed is effective for large-scale N-glycosylation site identification. Graphical abstract Proposed mechanism of glycopeptides enrichment using DEAE-Sepharose.

An OGA-Resistant Probe Allows Specific Visualization and Accurate Identification of O-GlcNAc-Modified Proteins in Cells.

O-linked ß-N-acetyl-glucosamine (O-GlcNAc) is an essential and ubiquitous post-translational modification present in nucleic and cytoplasmic proteins of multicellular eukaryotes. The metabolic chemical probes such as GlcNAc or GalNAc analogues bearing ketone or azide handles, in conjunction with bioorthogonal reactions, provide a powerful approach for detecting and identifying this modification. However, these chemical probes either enter multiple glycosylation pathways or have low labeling efficiency. Therefore, selective and potent probes are needed to assess this modification. We report here the development of a novel probe, 1,3,6-tri-O-acetyl-2-azidoacetamido-2,4-dideoxy-d-glucopyranose (Ac34dGlcNAz), that can be processed by the GalNAc salvage pathway and transferred by O-GlcNAc transferase (OGT) to O-GlcNAc proteins. Due to the absence of a hydroxyl group at C4, this probe is less incorporated into α/ß 4-GlcNAc or GalNAc containing glycoconjugates. Furthermore, the O-4dGlcNAz modification was resistant to the hydrolysis of O-GlcNAcase (OGA), which greatly enhanced the efficiency of incorporation for O-GlcNAcylation. Combined with a click reaction, Ac34dGlcNAz allowed the selective visualization of O-GlcNAc in cells and accurate identification of O-GlcNAc-modified proteins with LC-MS/MS. This probe represents a more potent and selective tool in tracking, capturing, and identifying O-GlcNAc-modified proteins in cells and cell lysates.

Improvement of core-fucosylated glycoproteome coverage via alternating HCD and ETD fragmentation.

UNLABELLED: Core-fucosylation (CF) plays important roles in regulating biological processes in eukaryotes. Alterations of CF-glycosites or CF-glycans in bodily fluids correlate with cancer development. Therefore, global research of protein core-fucosylation with an emphasis on proteomics can explain pathogenic and metastasis mechanisms and aid in the discovery of new potential biomarkers for early clinical diagnosis. In this study, a precise and high throughput method was established to identify CF-glycosites from human plasma. We found that alternating HCD and ETD fragmentation (AHEF) can provide a complementary method to discover CF-glycosites. A total of 407 CF-glycosites among 267 CF-glycoproteins were identified in a mixed sample made from six normal human plasma samples. Among the 407 CF-glycosites, 10 are without the N-X-S/T/C consensus motif, representing 2.5% of the total number identified. All identified CF-glycopeptide results from HCD and ETD fragmentation were filtered with neutral loss peaks and characteristic ions of GlcNAc from HCD spectra, which assured the credibility of the results. This study provides an effective method for CF-glycosites identification and a valuable biomarker reference for clinical research. BIOLOGICAL SIGNIFICANCE: CF-glycosytion plays an important role in regulating biological processes in eukaryotes. Alterations of the glycosites and attached CF-glycans are frequently observed in various types of cancers. Thus, it is crucial to develop a strategy for mapping human CF-glycosylation. Here, we developed a complementary method via alternating HCD and ETD fragmentation (AHEF) to analyze CF-glycoproteins. This strategy reveals an excellent complementarity of HCD and ETD in the analysis of CF-glycoproteins, and provides a valuable biomarker reference for clinical research.

Chemoenzymatic synthesis of the bacterial polysaccharide repeating unit undecaprenyl pyrophosphate and its analogs.

Polysaccharides are essential and immunologically relevant components of bacterial cell walls. These biomolecules can be found covalently attached to lipids (e.g., O-polysaccharide (PS) contains undecaprenyl and lipopolysaccharide (LPS) contains lipid A) or noncovalently associated with cell wells (e.g., capsular PS (CPS)). Although extensive genetic studies have indicated that the Wzy-dependent biosynthetic pathway is primarily responsible for producing such polysaccharides, in vitro biochemical studies are needed to determine, for example, which gene product is responsible for catalyzing each step in the pathway, and to reveal molecular details about the Wzx translocase, Wzy polymerase and O-PS chain-length determinant. Many of these biochemical studies require access to a structurally well-defined PS repeating unit undecaprenyl pyrophosphate (RU-PP-Und), the key building block in this pathway. We describe herein the chemoenzymatic synthesis of Escherichia coli (serotype O157) RU-PP-Und. This involves (i) chemical synthesis of precursor N-acetyl-D-galactosamine (GalNAc)-PP-Und (2 weeks) and (ii) enzymatic extension of the precursor to produce RU-PP-Und (2 weeks). Undecaprenyl phosphate and peracetylated GalNAc-1-phosphate are prepared from commercially available undecaprenol and peracetylated GalNAc. The chemical coupling of these two products, followed by structural confirmation (mass spectrometry and NMR) and deprotection, generates GalNAc-PP-Und. This compound is then sequentially modified by enzymes in the E. coli serotype O157 (E. coli O157) O-PS biosynthetic pathway. Three glycosyltransferases (GTs) are involved (WbdN, WbdO and WbdP) and they transfer glucose (Glc), L-fucose (L-Fuc) and N-acetylperosamine (PerNAc) onto GalNAc-PP-Und to form the intact RU-PP-Und in a stepwise manner. Final compounds and intermediates are confirmed by mass spectrometry. The procedure can be adapted to the synthesis of analogs with different PS or lipid moieties.

Characterizing non-hydrolyzing Neisseria meningitidis serogroup A UDP-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase using UDP-N-acetylmannosamine (UDP-ManNAc) and derivatives.

Neisseria meningitidis serogroup A non-hydrolyzing uridine 5'-diphosphate-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase (NmSacA) catalyzes the interconversion between UDP-GlcNAc and uridine 5'-diphosphate-N-acetylmannosamine (UDP-ManNAc). It is a key enzyme involved in the biosynthesis of the capsular polysaccharide [-6ManNAcα1-phosphate-]n of N. meningitidis serogroup A, one of the six serogroups (A, B, C, W-135, X, and Y) that account for most cases of N. meningitidis-caused bacterial septicemia and meningitis. N. meningitidis serogroup A is responsible for large epidemics in the developing world, especially in Africa. Here we report that UDP-ManNAc could be used as a substrate for C-terminal His6-tagged recombinant NmSacA (NmSacA-His6) in the absence of UDP-GlcNAc. NmSacA-His6 was activated by UDP-GlcNAc and inhibited by 2-acetamidoglucal and UDP. Substrate specificity study showed that NmSacA-His6 could tolerate several chemoenzymatically synthesized UDP-ManNAc derivatives as substrates although its activity was much lower than non-modified UDP-ManNAc. Homology modeling and molecular docking revealed likely structural determinants of NmSacA substrate specificity. This is the first detailed study of N. meningitidis serogroup A UDP-GlcNAc 2-epimerase.

Biochemical characterization of an α1,2-colitosyltransferase from Escherichia coli O55:H7.

Colitose, also known as 3,6-dideoxy-L-galactose or 3-deoxy-L-fucose, is one of only five naturally occurring 3,6-dideoxyhexoses. Colitose was found in lipopolysaccharide of a number of infectious bacteria, including Escherichia coli O55 & O111 and Vibrio cholera O22 & O139. To date, no colitosyltransferase (ColT) has been characterized, probably due to the inaccessibility of the sugar donor, GDP-colitose. In this study, starting with chemically prepared colitose, 94.6 mg of GDP-colitose was prepared via a facile and efficient one-pot two-enzyme system involving an L-fucokinase/GDP-L-Fuc pyrophosphorylase and an inorganic pyrophosphatase (EcPpA). WbgN, a putative ColT from E. coliO55:H5 was then cloned, overexpressed, purified and biochemically characterized by using GDP-colitose as a sugar donor. Activity assay and structural identification of the synthetic product clearly demonstrated that wbgN encodes an α1,2-ColT. Biophysical study showed that WbgN does not require metal ion, and is highly active at pH 7.5-9.0. In addition, acceptor specificity study indicated that WbgN exclusively recognizes lacto-N-biose (Galß1,3-GlcNAc). Most interestingly, it was found that WbgN exhibits similar activity toward GDP-l-Fuc (kcat/Km= 9.2 min(-1)mM(-1)) as that toward GDP-colitose (kcat/Km= 12 min(-1)mM(-1)). Finally, taking advantage of this, type 1 H-antigen was successfully synthesized in preparative scale.

Efficient Chemoenzymatic Synthesis of an N-glycan Isomer Library.

Quantification, characterization and biofunctional studies of N-glycans on proteins remain challenging tasks due to complexity, diversity and low abundance of these glycans. The availability of structurally defined N-glycans (especially isomers) libraries is essential to help on solving these tasks. We reported herein an efficient chemoenzymatic strategy, namely Core Synthesis/Enzymatic Extension (CSEE), for rapid production of diverse N-glycans. Starting with 5 chemically prepared building blocks, 8 N-glycan core structures containing one or two terminal N-acetyl-D-glucosamine (GlcNAc) residue(s) were chemically synthesized via consistent use of oligosaccharyl thioethers as glycosylation donors in the convergent fragment coupling strategy. Each of these core structures was then extended to 5 to 15 N-glycan sequences by enzymatic reactions catalyzed by 4 robust glycosyltransferases. Success in synthesizing N-glycans with Neu5Gc and core-fucosylation further expanded the ability of enzymatic extension. High performance liquid chromatography with an amide column enabled rapid and efficient purification (>98% purity) of N-glycans in milligram scales. A total of 73 N-glycans (63 isomers) were successfully prepared and characterized by MS2 and NMR. The CSEE strategy provides a practical approach for "mass production" of structurally defined N-glycans, which are important standards and probes for Glycoscience.

Convenient and Precise Strategy for Mapping N-Glycosylation Sites Using Microwave-Assisted Acid Hydrolysis and Characteristic Ions Recognition.

N-glycosylation is one of the most prevalence protein post-translational modifications (PTM) which is involved in several biological processes. Alternation of N-glycosylation is associated with cellular malfunction and development of disease. Thus, investigation of protein N-glycosylation is crucial for diagnosis and treatment of disease. Currently, deglycosylation with peptide N-glycosidase F is the most commonly used technique in N-glycosylation analysis. Additionally, a common error in N-glycosylation site identification, resulting from protein chemical deamidation, has largely been ignored. In this study, we developed a convenient and precise approach for mapping N-glycosylation sites utilizing with optimized TFA hydrolysis, ZIC-HILIC enrichment, and characteristic ions of N-acetylglucosamine (GlcNAc) from higher-energy collisional dissociation (HCD) fragmentation. Using this method, we identified a total of 257 N-glycosylation sites and 144 N-glycoproteins from healthy human serum. Compared to deglycosylation with endoglycosidase, this strategy is more convenient and efficient for large scale N-glycosylation sites identification and provides an important alternative approach for the study of N-glycoprotein function.

Efficient chemoenzymatic synthesis of novel galacto-N-biose derivatives and their sialylated forms.

Galacto-N-biose (GNB) derivatives were efficiently synthesized from galactose derivatives via a one-pot two-enzyme system containing two promiscuous enzymes from Bifidobacterium infantis: a galactokinase (BiGalK) and a d-galactosyl-ß1-3-N-acetyl-d-hexosamine phosphorylase (BiGalHexNAcP). Mono-sialyl and di-sialyl galacto-N-biose derivatives were then prepared using a one-pot two-enzyme system containing a CMP-sialic acid synthetase and an α2-3-sialyltransferase or an α2-6-sialyltransferase.