N-Glycosidase-carbohydrate-binding module fusion proteins as immobilized enzymes for protein deglycosylation

Rapid preparation of a glycan oxazoline and a homogeneously glycosylated antibody with an enzyme-immobilized monolithic column

Chemo-enzymatic glycan engineering is considered to be one of the most promising strategies to enhance efficiency in pharmaceutical research. However, it is assumed that this technology has limited industrial application for the production of biological therapeutics because of the high cost of the process. In this study, we developed a scheme for rapidly preparing a glycan oxazoline and a homogeneously glycosylated antibody. The enzyme-immobilized monolith and the flow chemistry-based approach enabled a glycan oxazoline and a homogeneously glycosylated antibody to be obtained at the gram scale from starting materials (sialylglycopeptide and heterogeneously glycosylated protein) within 2.5 h. This cost-effective scheme for obtaining a large amount of glycan donors and homogeneously glycosylated proteins in a short time will be helpful to implement glycan engineering technology for industrial purposes such as pharmaceutical production.

Spontaneous and site-specific immobilization of PNGase F via spy chemistry

Protein N-glycosylation plays a critical role in a wide range of biological processes, and aberrant N-glycosylation is frequently associated with various pathological states. For global N-glycosylation analysis, N-glycans are typically released from glycoproteins mediated by endoglycosidases, primarily peptide N-glycosidase F (PNGase F). However, conventional N-glycan release by in-solution PNGase F is time-consuming and nonreusable. Although some immobilization methods can save time and reduce the enzyme dosage, including affinity interaction and covalent binding, the immobilized PNGase F by these traditional methods may compromises the immobilized enzyme's stability and biofunction. Therefore, a new approach is urgently needed to firmly and steadily immobilize PNGase F. To meet this demand, we have developed a spontaneous and site-specific way to immobilize PNGase F onto magnetic nanoparticles via Spy chemistry. The magnetic nanoparticles were synthesized and modified with SpyTag as a solid surface. The PNGase F fused with SpyCatcher can then be site-specifically and covalently immobilized onto this solid phase, forming a firm isopeptide bond via self-catalysis between the SpyTag peptide and SpyCatcher. Importantly, the immobilization process mediated by mild spy chemistry does not result in PNGase F inactivation; and allows immobilized PNGase F to rapidly release various types of glycans (high-mannose, sialylated, and hybrid) from glycoproteins. Moreover, the immobilized PNGase F exhibited good deglycosylation activity and facilitated good reusability in consecutive reactions. Deglycosylation of clinical samples was completed by the immobilized PNGase F as fast as several minutes.

Site-specific, covalent immobilization of PNGase F on magnetic particles mediated by microbial transglutaminase

In the workflow of global N-glycosylation analysis, endoglycosidase-mediated removal of glycans from glycoproteins is an essential and rate-limiting step. Peptide-N-glycosidase F (PNGase F) is the most appropriate and efficient endoglycosidase for the removal of N-glycans from glycoproteins prior to analysis. Due to the high demand for PNGase F in both basic and industrial research, convenient and efficient methods are urgently needed to generate PNGase F, preferably in the immobilized form to solid phases. However, there is no integrated approach to implement both efficient expression, and site-specific immobilization of PNGase F. Herein, efficient production of PNGase F with a glutamine tag in Escherichia coli and site-specific covalent immobilization of PNGase F with this special tag via microbial transglutaminase (MTG) is described. PNGase F was fused with a glutamine tag to facilitate the co-expression of proteins in the supernatant. The glutamine tag was covalently and site-specifically transformed to primary amine-containing magnetic particles, mediated by MTG, to immobilize PNGase F. Immobilized PNGase F could deglycosylate substrates with identical enzymatic performance to that of the soluble counterpart, and exhibit good reusability and thermal stability. Moreover, the immobilized PNGase F could also be applied to clinical samples, including serum and saliva.

Microwave-induced biocatalytic reactions toward medicinally important compounds

Microwaves in the presence of enzymes are used to execute a number of reactions for the preparation of biologically active compounds. The success of microwave-induced enzymatic reactions depends on frequencies, field strength, waveform, duration, and modulation of the exposure. Enzymes under microwave irradiation become activated and this activation is sufficient to investigate simple to complex reactions that were not reported under these reaction conditions before. Enzymatic catalysis together with microwave technology and solvent-free chemical reaction is a nature-friendly procedure. The most interesting reactions that are performed by enzymes in the microwave are documented here with reference to examples that are related to medicinally active molecules.

Immobilized peptide-N-glycosidase F onto magnetic nanoparticles: A biotechnological tool for protein deglycosylation under native conditions

The elucidation of glycans biological function is essential to understand their role in biological processes, both normal and pathological. Immobilized glycoenzymes are excellent tools for this purpose as they can selectively release glycans from glycoproteins without altering their backbone. They can be easily removed from the reaction mixture avoiding their interference in subsequent experiments. Here, we describe the immobilization of peptide-N-glycosidase F (PNGase F) onto silica magnetic nanoparticles with immobilization yields of 86% and activity yields of 12%. Immobilized PNGase F showed higher thermal stability than its soluble counterpart, and could be reused for at least seven deglycosylation cycles. It was efficient in the deglycosylation of several glycoproteins (ribonuclease B, bovine fetuin, and ovalbumin) and a protein lysate from the parasite Fasciola hepatica under native conditions, with similar performance to that of the soluble enzyme. Successful deglycosylation was evidenced by a decrease in specific lectin recognition of the glycoproteins (40%-80%). Moreover, deglycosylated F. hepatica lysate allowed us to confirm the role of parasite N-glycans in the inhibition of the lipopolysaccharide-induced maturation of dendritic cells. Immobilized PNGase F probed to be a robust biotechnological tool for deglycosylation of glycoproteins and complex biological samples under native conditions.

Affinity to cellulose is a shared property among coiled-coil domains of intermediate filaments and prokaryotic intermediate filament-like proteins

Coiled-coil domains of intermediate filaments (IF) and prokaryotic IF-like proteins enable oligomerisation and filamentation, and no additional function is ascribed to these coiled-coil domains. However, an IF-like protein from Streptomyces reticuli was reported to display cellulose affinity. We demonstrate that cellulose affinity is an intrinsic property of the IF-like proteins FilP and Scy and the coiled-coil protein DivIVA from the genus Streptomyces. Furthermore, IF-like proteins and DivIVA from other prokaryotic species and metazoan IF display cellulose affinity despite having little sequence homology. Cellulose affinity-based purification is utilised to isolate native FilP protein from the whole cell lysate of S. coelicolor. Moreover, cellulose affinity allowed for the isolation of IF and IF-like protein from the whole cell lysate of C. crescentus and a mouse macrophage cell line. The binding to cellulose is mediated by certain combinations of coiled-coil domains, as demornstrated for FilP and lamin. Fusions of target proteins to cellulose-binding coiled-coil domains allowed for cellulose-based protein purification. The data presented show that cellulose affinity is a novel function of certain coiled-coil domains of IF and IF-like proteins from evolutionary diverse species.

Expression system for structural and functional studies of human glycosylation enzymes

Vertebrate glycoproteins and glycolipids are synthesized in complex biosynthetic pathways localized predominantly within membrane compartments of the secretory pathway. The enzymes that catalyze these reactions are exquisitely specific, yet few have been extensively characterized because of challenges associated with their recombinant expression as functional products. We used a modular approach to create an expression vector library encoding all known human glycosyltransferases, glycoside hydrolases, and sulfotransferases, as well as other glycan-modifying enzymes. We then expressed the enzymes as secreted catalytic domain fusion proteins in mammalian and insect cell hosts, purified and characterized a subset of the enzymes, and determined the structure of one enzyme, the sialyltransferase ST6GalNAcII. Many enzymes were produced at high yields and at similar levels in both hosts, but individual protein expression levels varied widely. This expression vector library will be a transformative resource for recombinant enzyme production, broadly enabling structure-function studies and expanding applications of these enzymes in glycochemistry and glycobiology.

Structural, mutagenic and in silico studies of xyloglucan fucosylation in Arabidopsis thaliana suggest a water-mediated mechanism

The mechanistic underpinnings of the complex process of plant polysaccharide biosynthesis are poorly understood, largely because of the resistance of glycosyltransferase (GT) enzymes to structural characterization. In Arabidopsis thaliana, a glycosyl transferase family 37 (GT37) fucosyltransferase 1 (AtFUT1) catalyzes the regiospecific transfer of terminal 1,2-fucosyl residues to xyloglucan side chains - a key step in the biosynthesis of fucosylated sidechains of galactoxyloglucan. We unravel the mechanistic basis for fucosylation by AtFUT1 with a multipronged approach involving protein expression, X-ray crystallography, mutagenesis experiments and molecular simulations. Mammalian cell culture expressions enable the sufficient production of the enzyme for X-ray crystallography, which reveals the structural architecture of AtFUT1 in complex with bound donor and acceptor substrate analogs. The lack of an appropriately positioned active site residue as a catalytic base leads us to propose an atypical water-mediated fucosylation mechanism facilitated by an H-bonded network, which is corroborated by mutagenesis experiments as well as detailed atomistic simulations.

Growth modulation effects of CBM2a under the control of AtEXP4 and CaMV35S promoters in Arabidopsis thaliana, Nicotiana tabacum and Eucalyptus camaldulensis

The expression of cell-wall-targeted Carbohydrate Binding Modules (CBMs) can alter cell wall properties and modulate growth and development in plants such as tobacco and potato. CBM2a identified in xylanase 10A from Cellulomonas fimi is of particular interest for its ability to bind crystalline cellulose. However, its potential for promoting plant growth has not been explored. In this work, we tested the ability of CBM2a to promote growth when expressed using both CaMV35S and a vascular tissue-specific promoter derived from Arabidopsis expansin4 (AtEXP4) in three plant species: Arabidopsis, Nicotiana tabacum and Eucalyptus camaldulensis. In Arabidopsis, the expression of AtEXP4pro:CBM2a showed trends for growth promoting effects including the increase of root and hypocotyl lengths and the enlargements of the vascular xylem area, fiber cells and vessel cells. However, in N. tabacum, the expression of CBM2a under the control of either CaMV35S or AtEXP4 promoter resulted in subtle changes in the plant growth, and the thickness of secondary xylem and vessel and fiber cell sizes were generally reduced in the transgenic lines with AtEXP4pro:CBM2a. In Eucalyptus, while transgenics expressing CaMV35S:CBM2a showed very subtle changes compared to wild type, those transgenics with AtEXP4pro:CBM2a showed increases in plant height, enlargement of xylem areas and xylem fiber and vessel cells. These data provide comparative effects of expressing CBM2a protein in different plant species, and this finding can be applied for plant biomass improvement.

Substrate recognition and catalysis by GH47 α-mannosidases involved in Asn-linked glycan maturation in the mammalian secretory pathway

Maturation of Asn-linked oligosaccharides in the eukaryotic secretory pathway requires the trimming of nascent glycan chains to remove all glucose and several mannose residues before extension into complex-type structures on the cell surface and secreted glycoproteins. Multiple glycoside hydrolase family 47 (GH47) α-mannosidases, including endoplasmic reticulum (ER) α-mannosidase I (ERManI) and Golgi α-mannosidase IA (GMIA), are responsible for cleavage of terminal α1,2-linked mannose residues to produce uniquely trimmed oligomannose isomers that are necessary for ER glycoprotein quality control and glycan maturation. ERManI and GMIA have similar catalytic domain structures, but each enzyme cleaves distinct residues from tribranched oligomannose glycan substrates. The structural basis for branch-specific cleavage by ERManI and GMIA was explored by replacing an essential enzyme-bound Ca²⁺ ion with a lanthanum (La³⁺) ion. This ion swap led to enzyme inactivation while retaining high-affinity substrate interactions. Cocrystallization of La³⁺-bound enzymes with Man₉GlcNAc₂ substrate analogs revealed enzyme-substrate complexes with distinct modes of glycan branch insertion into the respective enzyme active-site clefts. Both enzymes had glycan interactions that extended across the entire glycan structure, but each enzyme engaged a different glycan branch and used different sets of glycan interactions. Additional mutagenesis and time-course studies of glycan cleavage probed the structural basis of enzyme specificity. The results provide insights into the enzyme catalytic mechanisms and reveal structural snapshots of the sequential glycan cleavage events. The data also indicate that full steric access to glycan substrates determines the efficiency of mannose-trimming reactions that control the conversion to complex-type structures in mammalian cells.

Recent advances in immobilization strategies for glycosidases

Glycans play important biological roles in cell-to-cell interactions, protection against pathogens, as well as in proper protein folding and stability, and are thus interesting targets for scientists. Although their mechanisms of action have been widely investigated and hypothesized, their biological functions are not well understood due to the lack of deglycosylation methods for large-scale isolation of these compounds. Isolation of glycans in their native state is crucial for the investigation of their biological functions. However, current enzymatic and chemical deglycosylation techniques require harsh pretreatment and reaction conditions (high temperature and use of detergents) that hinder the isolation of native glycan structures. Indeed, the recent isolation of new endoglycosidases that are able to cleave a wider variety of linkages and efficiently hydrolyze native proteins has opened up the opportunity to elucidate the biological roles of a higher variety of glycans in their native state. As an example, our research group recently isolated a novel Endo-β-N-acetylglucosaminidase from Bifidobacterium longum subsp. infantis ATCC 15697 (EndoBI-1) that cleaves N-N'-diacetyl chitobiose moieties found in the N-linked glycan (N-glycan) core of high mannose, hybrid, and complex N-glycans. This enzyme is also active on native proteins, which enables native glycan isolation, a key advantage when evaluating their biological activities. Efficient, stable, and economically viable enzymatic release of N-glycans requires the selection of appropriate immobilization strategies. In this review, we discuss the state-of-the-art of various immobilization techniques (physical adsorption, covalent binding, aggregation, and entrapment) for glycosidases, as well as their potential substrates and matrices. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:104-112, 2017.

Protein O-Glucosyltransferase 1 (POGLUT1) Promotes Mouse Gastrulation through Modification of the Apical Polarity Protein CRUMBS2

Crumbs family proteins are apical transmembrane proteins with ancient roles in cell polarity. Mouse Crumbs2 mutants arrest at midgestation with abnormal neural plate morphology and a deficit of mesoderm caused by defects in gastrulation. We identified an ENU-induced mutation, wsnp, that phenocopies the Crumbs2 null phenotype. We show that wsnp is a null allele of Protein O-glucosyltransferase 1 (Poglut1), which encodes an enzyme previously shown to add O-glucose to EGF repeats in the extracellular domain of Drosophila and mammalian Notch, but the role of POGLUT1 in mammalian gastrulation has not been investigated. As predicted, we find that POGLUT1 is essential for Notch signaling in the early mouse embryo. However, the loss of mouse POGLUT1 causes an earlier and more dramatic phenotype than does the loss of activity of the Notch pathway, indicating that POGLUT1 has additional biologically relevant substrates. Using mass spectrometry, we show that POGLUT1 modifies EGF repeats in the extracellular domain of full-length mouse CRUMBS2. CRUMBS2 that lacks the O-glucose modification fails to be enriched on the apical plasma membrane and instead accumulates in the endoplasmic reticulum. The data demonstrate that CRUMBS2 is the target of POGLUT1 for the gastrulation epithelial-to-mesenchymal transitions (EMT) and that all activity of CRUMBS2 depends on modification by POGLUT1. Mutations in human POGLUT1 cause Dowling-Degos Disease, POGLUT1 is overexpressed in a variety of tumor cells, and mutations in the EGF repeats of human CRUMBS proteins are associated with human congenital nephrosis, retinitis pigmentosa and retinal degeneration, suggesting that O-glucosylation of CRUMBS proteins has broad roles in human health.

Fusion of a xylan-binding module to gluco-oligosaccharide oxidase increases activity and promotes stable immobilization

The xylan-binding module Clostridium thermocellum CBM22A was successfully fused to a gluco-oligosaccharide oxidase, GOOX-VN, from Sarocladium strictum via a short TP linker, allowing the fused protein to effectively bind different xylans. The presence of the CtCBM22A at the N-terminal of GOOX-VN increased catalytic activity on mono- and oligo-saccharides by 2-3 fold while not affecting binding affinity to these substrates. Notably, both GOOX-VN and its CBM fusion also showed oxidation of xylo-oligosaccharides with degrees of polymerization greater than six. Whereas fusion to CtCBM22A did not alter the thermostability of GOOX-VN or reduce substrate inhibition, CtCBM22A_GOOX-VN could be immobilized to insoluble oat spelt xylan while retaining wild-type activity. QCM-D analysis showed that the fused enzyme remained bound during oxidation. These features could be harnessed to generate hemicellulose-based biosensors that detect and quantify the presence of different oligosaccharides.

Cellulosome-based, Clostridium-derived multi-functional enzyme complexes for advanced biotechnology tool development: advances and applications

The cellulosome is one of nature's most elegant and elaborate nanomachines and a key biological and biotechnological macromolecule that can be used as a multi-functional protein complex tool. Each protein module in the cellulosome system is potentially useful in an advanced biotechnology application. The high-affinity interactions between the cohesin and dockerin domains can be used in protein-based biosensors to improve both sensitivity and selectivity. The scaffolding protein includes a carbohydrate-binding module (CBM) that attaches strongly to cellulose substrates and facilitates the purification of proteins fused with the dockerin module through a one-step CBM purification method. Although the surface layer homology (SLH) domain of CbpA is not present in other strains, replacement of the cell surface anchoring domain allows a foreign protein to be displayed on the surface of other strains. The development of a hydrolysis enzyme complex is a useful strategy for consolidated bioprocessing (CBP), enabling microorganisms with biomass hydrolysis activity. Thus, the development of various configurations of multi-functional protein complexes for use as tools in whole-cell biocatalyst systems has drawn considerable attention as an attractive strategy for bioprocess applications. This review provides a detailed summary of the current achievements in Clostridium-derived multi-functional complex development and the impact of these complexes in various areas of biotechnology.

Enzymatic basis for N-glycan sialylation: structure of rat α2,6-sialyltransferase (ST6GAL1) reveals conserved and unique features for glycan sialylation

Glycan structures on glycoproteins and glycolipids play critical roles in biological recognition, targeting, and modulation of functions in animal systems. Many classes of glycan structures are capped with terminal sialic acid residues, which contribute to biological functions by either forming or masking glycan recognition sites on the cell surface or secreted glycoconjugates. Sialylated glycans are synthesized in mammals by a single conserved family of sialyltransferases that have diverse linkage and acceptor specificities. We examined the enzymatic basis for glycan sialylation in animal systems by determining the crystal structures of rat ST6GAL1, an enzyme that creates terminal α2,6-sialic acid linkages on complex-type N-glycans, at 2.4 Å resolution. Crystals were obtained from enzyme preparations generated in mammalian cells. The resulting structure revealed an overall protein fold broadly resembling the previously determined structure of pig ST3GAL1, including a CMP-sialic acid-binding site assembled from conserved sialylmotif sequence elements. Significant differences in structure and disulfide bonding patterns were found outside the sialylmotif sequences, including differences in residues predicted to interact with the glycan acceptor. Computational substrate docking and molecular dynamics simulations were performed to predict and evaluate the CMP-sialic acid donor and glycan acceptor interactions, and the results were compared with kinetic analysis of active site mutants. Comparisons of the structure with pig ST3GAL1 and a bacterial sialyltransferase revealed a similar positioning of donor, acceptor, and catalytic residues that provide a common structural framework for catalysis by the mammalian and bacterial sialyltransferases.

Identification of C-terminal phosphorylation sites of N-formyl peptide receptor-1 (FPR1) in human blood neutrophils

Accumulation, activation, and control of neutrophils at inflammation sites is partly driven by N-formyl peptide chemoattractant receptors (FPRs). Occupancy of these G-protein-coupled receptors by formyl peptides has been shown to induce regulatory phosphorylation of cytoplasmic serine/threonine amino acid residues in heterologously expressed recombinant receptors, but the biochemistry of these modifications in primary human neutrophils remains relatively unstudied. FPR1 and FPR2 were partially immunopurified using antibodies that recognize both receptors (NFPRa) or unphosphorylated FPR1 (NFPRb) in dodecylmaltoside extracts of unstimulated and N-formyl-Met-Leu-Phe (fMLF) + cytochalasin B-stimulated neutrophils or their membrane fractions. After deglycosylation and separation by SDS-PAGE, excised Coomassie Blue-staining bands (∼34,000 Mr) were tryptically digested, and FPR1, phospho-FPR1, and FPR2 content was confirmed by peptide mass spectrometry. C-terminal FPR1 peptides (Leu(312)-Arg(322) and Arg(323)-Lys(350)) and extracellular FPR1 peptide (Ile(191)-Arg(201)) as well as three similarly placed FPR2 peptides were identified in unstimulated and fMLF + cytochalasin B-stimulated samples. LC/MS/MS identified seven isoforms of Ala(323)-Lys(350) only in the fMLF + cytochalasin B-stimulated sample. These were individually phosphorylated at Thr(325), Ser(328), Thr(329), Thr(331), Ser(332), Thr(334), and Thr(339). No phospho-FPR2 peptides were detected. Cytochalasin B treatment of neutrophils decreased the sensitivity of fMLF-dependent NFPRb recognition 2-fold, from EC50 = 33 ± 8 to 74 ± 21 nM. Our results suggest that 1) partial immunopurification, deglycosylation, and SDS-PAGE separation of FPRs is sufficient to identify C-terminal FPR1 Ser/Thr phosphorylations by LC/MS/MS; 2) kinases/phosphatases activated in fMLF/cytochalasin B-stimulated neutrophils produce multiple C-terminal tail FPR1 Ser/Thr phosphorylations but have little effect on corresponding FPR2 sites; and 3) the extent of FPR1 phosphorylation can be monitored with C-terminal tail FPR1-phosphospecific antibodies.

Cellulose affinity purification of fusion proteins tagged with fungal family 1 cellulose-binding domain

N- or C-terminal fusions of red-fluorescent protein (RFP) with various fungal cellulose-binding domains (CBDs) belonging to carbohydrate binding module (CBM) family 1 were expressed in a Pichia pastoris expression system, and the resulting fusion proteins were used to examine the feasibility of large-scale affinity purification of CBD-tagged proteins on cellulose columns. We found that RFP fused with CBD from Trichoderma reesei CBHI (CBD(Tr)(CBHI)) was expressed at up to 1.2g/l in the culture filtrate, which could be directly injected into the cellulose column. The fusion protein was tightly adsorbed on the cellulose column in the presence of a sufficient amount of ammonium sulfate and was efficiently eluted with pure water. Bovine serum albumin (BSA) was not captured under these conditions, whereas both BSA and the fusion protein were adsorbed on a phenyl column, indicating that the cellulose column can be used for the purification of not only hydrophilic proteins but also for hydrophobic proteins. Recovery of various fusion proteins exceeded 80%. Our results indicate that protein purification by expression of a target protein as a fusion with a fungal family 1 CBD tag in a yeast expression system, followed by affinity purification on a cellulose column, is simple, effective and easily scalable.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for the period 2005-2006

This review is the fourth update of the original review, published in 1999, on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2006. The review covers fundamental studies, fragmentation of carbohydrate ions, method developments, and applications of the technique to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, glycated proteins, glycolipids from bacteria, glycosides, and various other natural products. There is a short section on the use of MALDI-TOF mass spectrometry for the study of enzymes involved in glycan processing, a section on industrial processes, particularly the development of biopharmaceuticals and a section on the use of MALDI-MS to monitor products of chemical synthesis of carbohydrates. Large carbohydrate-protein complexes and glycodendrimers are highlighted in this final section.

Matrix-assisted laser desorption/ionization on-target method for the investigation of oligosaccharides and glycosylation sites in glycopeptides and glycoproteins

The significance of glycoproteins in living systems instigates the ceaseless expansion of new techniques and procedures for the analysis of biological samples. Many of these applications are focused on improving the detection limit of analyzed material. In a previous study, we described a procedure for the detection of oligosaccharides cleaved from tryptic glycopeptides. Treatment of deglycosylated fractions with phenylhydrazine gave rise to peaks consistent with labeled glycans, and both types of compounds--deglycosylated peptides and oligosaccharides--were recorded from one spot and observed in one matrix-assisted laser desorption/ionization (MALDI) mass spectrum for the first time. Here, we added an additional step to this simple procedure of deglycosylating glycopeptides directly from the target spot of the first analyzed glycosylated peptides. For the purpose of this new study, a mixture of 2-aza-2-thiothymine and phenylhydrazine hydrochloride showed to be an excellent matrix for glycopeptides, oligosaccharides, deglycosylated peptides and moreover it allowed PNGaseF to be active enough to cleave oligosaccharides from peptides. The efficiency of this procedure is demonstrated on a series of intact glycoproteins and on the analysis of tryptic peptides obtained from IgG and total mouse serum. This one-step on-target deglycosylation method with subsequent derivatization on the same spot makes MALDI-MS analyses of glycopeptides fast, simple and accessible for biological samples, where classical procedures cannot produce useful results.