Engineering of a chitin deacetylase to generate tailor-made chitosan polymers.

Chitin deacetylases (CDAs) emerge as a valuable tool to produce chitosans with a nonrandom distribution of N-acetylglucosamine (GlcNAc) and glucosamine (GlcN) units. We hypothesized before that CDAs tend to bind certain sequences within the substrate matching their subsite preferences for either GlcNAc or GlcN units. Thus, they deacetylate or N-acetylate their substrates at nonrandom positions. To understand the molecular basis of these preferences, we analyzed the binding site of a CDA from Pestalotiopsis sp. (PesCDA) using a detailed activity screening of a site-saturation mutagenesis library. In addition, molecular dynamics simulations were conducted to get an in-depth view of crucial interactions along the binding site. Besides elucidating the function of several amino acids, we were able to show that only 3 residues are responsible for the highly specific binding of PesCDA to oligomeric substrates. The preference to bind a GlcNAc unit at subsite -2 and -1 can mainly be attributed to N75 and H199, respectively. Whereas an exchange of N75 at subsite -2 eliminates enzyme activity, H199 can be substituted with tyrosine to increase the GlcN acceptance at subsite -1. This change in substrate preference not only increases enzyme activity on certain substrates and changes composition of oligomeric products but also significantly changes the pattern of acetylation (PA) when N-acetylating polyglucosamine. Consequently, we could clearly show how subsite preferences influence the PA of chitosans produced with CDAs.

Control of Substrate Conformation by Hydrogen Bonding in a Retaining ß-Endoglycosidase.

Bacterial ß-glycosidases are hydrolytic enzymes that depolymerize polysaccharides such as ß-cellulose, ß-glucans and ß-xylans from different sources, offering diverse biomedical and industrial uses. It has been shown that a conformational change of the substrate, from a relaxed 4 C1 conformation to a distorted 1 S3 /1,4 B conformation of the reactive sugar, is necessary for catalysis. However, the molecular determinants that stabilize the substrate's distortion are poorly understood. Here we use quantum mechanics/molecular mechanics (QM/MM)-based molecular dynamics methods to assess the impact of the interaction between the reactive sugar, i. e. the one at subsite -1, and the catalytic nucleophile (a glutamate) on substrate conformation. We show that the hydrogen bond involving the C2 exocyclic group and the nucleophile controls substrate conformation: its presence preserves sugar distortion, whereas its absence (e.g. in an enzyme mutant) knocks it out. We also show that 2-deoxy-2-fluoro derivatives, widely used to trap the reaction intermediates by X-ray crystallography, reproduce the conformation of the hydrolysable substrate at the experimental conditions. These results highlight the importance of the 2-OH⋅⋅⋅nucleophile interaction in substrate recognition and catalysis in endo-glycosidases and can inform mutational campaigns aimed to search for more efficient enzymes.

Novel α-mannose-functionalized poly(ß-amino ester) nanoparticles as mRNA vaccines with increased antigen presenting cell selectivity in the spleen.

mRNA vaccination has emerged as a prominent therapy for the future of medicine. Despite the colossal advance in this technology and worldwide efficacy proof (ca. COVID vaccines), mRNA carriers still lack cell/tissue specificity, leading to possible side effects, and reduced efficacy among others. Herein we make use of the ubiquitous affinity of antigen-presenting cells (APC)s for glycosides to achieve specific targeting. To achieve this goal, we designed a new generation of α-mannosyl functionalized oligopeptide-terminated poly(ß-aminoester). Fine formulation of these polymers with mRNA resulted in nanoparticles decorated with surface-exposed α-mannoses with sizes around 180 nm and positive surface charge. Notably, these particles maintained their properties after freeze-drying and subsequent redispersion. Finally, our mRNA carriers preferentially targeted and transfected APCs in vitro and in vivo. In conclusion, we demonstrated, at a preclinical level, that the mannose functionalization enables more selective targeting of APCs and, thus, these polymer and nanoparticles are candidates for a new generation of mRNA immunotherapy vaccines.

Chloroplast engineering of the green microalgae Chlamydomonas reinhardtii for the production of HAA, the lipid moiety of rhamnolipid biosurfactants.

Hydroxyalkanoyloxyalkanoates (HAA) are lipidic surfactants with a number of potential applications, but more remarkably, they are the biosynthetic precursors of rhamnolipids (RL), which are preferred biosurfactants thanks to their excellent physicochemical properties, biological activities, and environmental biodegradability. Because the natural highest producer of RLs is the pathogenic bacterium Pseudomonas aeruginosa, important efforts have been dedicated to transfer production to heterologous non-pathogenic microorganisms. Unicellular photosynthetic microalgae are emerging as important hosts for sustainable industrial biotechnology due to their ability to transform CO2 efficiently into biomass and bioproducts of interest. Here, we have explored the potential of the eukaryotic green microalgae Chlamydomonas reinhardtii as a chassis to produce RLs. Chloroplast genome engineering allowed the stable functional expression of the gene encoding RhlA acyltransferase from P. aeruginosa, an enzyme catalyzing the condensation of two 3-hydroxyacyl acid intermediaries in the fatty acid synthase cycle, to produce HAA. Four congeners of varying chain lengths were identified and quantified by UHPLC-QTOF mass spectrometry and gas chromatography, including C10-C10 and C10-C8, and the less abundant C10-C12 and C10-C6 congeners. HAA was present in the intracellular fraction, but also showed increased accumulation in the extracellular medium. Moreover, HAA production was also observed under photoautotrophic conditions based on atmospheric CO2. These results establish that RhlA is active in the chloroplast and is able to produce a new pool of HAA in a eukaryotic host. Subsequent engineering of microalgal strains should contribute to the development of an alternative clean, safe and cost-effective platform for the sustainable production of RLs.

Developing a single-stage continuous process strategy for vitamin B12 production with Propionibacterium freudenreichii.

BACKGROUND: Vitamin B12 is a widely used compound in the feed and food, healthcare and medical industries that can only be produced by fermentation because of the complexity of its chemical synthesis. Besides, the use of Generally Recognized as Safe (GRAS) and Qualified Presumption of Safety (QPS) microorganisms, like Propionibacterium freudenreichii, especially non-GMO wild-type producers, are becoming an interesting alternative in markets where many final consumers have high health and ecological awareness. In this study, the production of vitamin B12 using the Propionibacterium freudenreichii NBRC 12391 wild-type strain was characterized and optimized in shake flasks before assessing several scale-up strategies. RESULTS: Initial results established that: (i) agitation during the early stages of the culture had an inhibitory effect on the volumetric production, (ii) 5,6-dimethylbenzimidazole (DMBI) addition was necessary for vitamin B12 production, and (iii) kinetics of vitamin B12 accumulation were dependent on the induction time when DMBI was added. When scaling up in a bioreactor, both batch and fed-batch bioprocesses proved unsuitable for obtaining high volumetric productivities mainly due to carbon source limitation and propionic acid inhibition, respectively. To overcome these drawbacks, an anaerobic single-phase continuous bioprocess strategy was developed. This culture strategy was maintained stable during more than 5 residence times in two independent cultures, resulting in 5.7-fold increase in terms of volumetric productivity compared to other scale-up strategies. CONCLUSION: Overall, compared to previously reported strategies aimed to reduce propionic acid inhibition, a less complex anaerobic single-phase continuous and more scalable bioprocess was achieved.

Controlled processivity in glycosyltransferases: A way to expand the enzymatic toolbox.

Glycosyltransferases (GT) catalyse the biosynthesis of complex carbohydrates which are the most abundant group of molecules in nature. They are involved in several key mechanisms such as cell signalling, biofilm formation, host immune system invasion or cell structure and this in both prokaryotic and eukaryotic cells. As a result, research towards complete enzyme mechanisms is valuable to understand and elucidate specific structure-function relationships in this group of molecules. In a next step this knowledge could be used in GT protein engineering, not only for rational drug design but also for multiple biotechnological production processes, such as the biosynthesis of hyaluronan, cellooligosaccharides or chitooligosaccharides. Generation of these poly- and/or oligosaccharides is possible due to a common feature of several of these GTs: processivity. Enzymatic processivity has the ability to hold on to the growing polymer chain and some of these GTs can even control the number of glycosyl transfers. In a first part, recent advances in understanding the mechanism of various processive enzymes are discussed. To this end, an overview is given of possible engineering strategies for the purpose of new industrial and fundamental applications. In the second part of this review, we focused on specific chain length-controlling mechanisms, i.e., key residues or conserved regions, and this for both eukaryotic and prokaryotic enzymes.

Characterization of a Glycolipid Synthase Producing α-Galactosylceramide in Bacteroides fragilis.

Glycolipids are complex molecules involved in important cellular processes. Among them, the glycosphingolipid α-galactosylceramide has proven to be of interest in biomedicine for its immunostimulatory capabilities. Given its structural requirements, the use of ceramide glycosyltransferase enzymes capable of synthesizing this molecule under in vivo or in vitro conditions is a potential production strategy. Several GT4 enzymes from Bacteroides fragilis were considered as potential candidates in addition to the known BF9343_3149, but only this one showed glycolipid synthase activity. The enzyme was expressed as a SUMO fusion protein to produce soluble protein. It is a non-processive glycosyltransferase that prefers UDP-Gal over UDP-Glc as a donor substrate, and maximum activity was found at pH 7.3 and around 30-35 °C. It does not require metal cations for activity as other GT4 enzymes, but Zn2+ inactivates the enzyme. The reaction occurs when the ceramide lipid acceptor is solubilized with BSA (100% conversion) but not when it is presented in mixed micelles, and anionic lipids do not increase activity, as in other membrane-associated glycolipid synthases. Further protein engineering to increase stability and activity can make feasible the enzymatic synthesis of α-GalCer for biomedical applications.

Bioprocess Strategies for Vitamin B12 Production by Microbial Fermentation and Its Market Applications.

Vitamin B12 is a widely used compound in the feed and food, healthcare and medical industries that can only be produced by fermentation because of the complexity of its chemical synthesis. For this reason, finding better producer strains and optimizing their bioprocesses have been the main focus of industrial producers over the last few decades. In this review, we initially provide a historical overview of vitamin B12 research and the main biosynthetic characteristics of the two microorganism families typically used for its industrial production: several strains of Propionibacterium freudenreichii and strains related to Pseudomonas denitrificans. Later, a complete summary of the current state of vitamin B12 industrial production as well as the main advances and challenges for improving it is detailed, with a special focus on bioprocess optimization, which aims not only to increase production but also sustainability. In addition, a comprehensive list of the most important and relevant patents for the present industrial strains is provided. Finally, the potential applications of vitamin B12 in different markets are discussed.

Integrative structure determination reveals functional global flexibility for an ultra-multimodular arabinanase.

AbnA is an extracellular GH43 α-L-arabinanase from Geobacillus stearothermophilus, a key bacterial enzyme in the degradation and utilization of arabinan. We present herein its full-length crystal structure, revealing the only ultra-multimodular architecture and the largest structure to be reported so far within the GH43 family. Additionally, the structure of AbnA appears to contain two domains belonging to new uncharacterized carbohydrate-binding module (CBM) families. Three crystallographic conformational states are determined for AbnA, and this conformational flexibility is thoroughly investigated further using the "integrative structure determination" approach, integrating molecular dynamics, metadynamics, normal mode analysis, small angle X-ray scattering, dynamic light scattering, cross-linking, and kinetic experiments to reveal large functional conformational changes for AbnA, involving up to ~100 Å movement in the relative positions of its domains. The integrative structure determination approach demonstrated here may apply also to the conformational study of other ultra-multimodular proteins of diverse functions and structures.

Enzymatic Hydrolysis of Human Milk Oligosaccharides. The Molecular Mechanism of Bifidobacterium Bifidum Lacto-N-biosidase.

Bifidobacterium bifidum lacto-N-biosidase (LnbB) is a critical enzyme for the degradation of human milk oligosaccharides in the gut microbiota of breast-fed infants. Guided by recent crystal structures, we unveil its molecular mechanism of catalysis using QM/MM metadynamics. We show that the oligosaccharide substrate follows 1 S 3/1,4 B → [4 E]‡ → 4 C 1/4 H 5 and 4 C 1/4 H 5 → [4 E/4 H 5]‡ → 1,4 B conformational itineraries for the two successive reaction steps, with reaction free energy barriers in agreement with experiments. The simulations also identify a critical histidine (His263) that switches between two orientations to modulate the pK a of the acid/base residue, facilitating catalysis. The reaction intermediate of LnbB is best depicted as an oxazolinium ion, with a minor population of neutral oxazoline. The present study sheds light on the processing of oligosaccharides of the early life microbiota and will be useful for the engineering of LnbB and similar glycosidases for biocatalysis.

The use of oxygen as a possible screening biomarker for the diagnosis of chronic fatigue

Background: The aim of this study was to verify whether the mean percentage of oxygen use in the aerobic-anaerobic transition phase or isocapnic buffering (IB) was lower in women with chronic fatigue syndrome (CFS) compared to healthy women, and if this variable could be used as a screening biomarker for the diagnosis of CFSMethodsA cross-sectional study was conducted. Forty-four adult women (22 with CFS and 22 healthy) performed a cycle ergometer stress test with gas analyser (CPET). Maximum oxygen consumption (V˙O2 max), oxygen consumption at the anaerobic threshold (V˙O2 at Vt2), maximum ventilatory volume (V˙E max), time of maintenance of the isocapnic buffering phase (IB duration), and mean percentage of oxygen use in isocapnic buffering phase (% O2 use in IB) were analyzed. Data were explored from a principal component analysis. Groups were matched by propensity score to be mismatched in BMI and a comparison of means and medians was performed. A logistic regression model was built to predict the probability of CFS.ResultsThe mean and median values of the variables obtained in the CPET was significantly higher in the healthy group compared to the CFS. In the logistic regression model, VO2 max, IB duration, and mean % of O2 use in IB were selected as predictors. The sensitivity and specificity were greater than 90%.ConclusionThe combination of the factors V˙O2 max, IB duration, and mean % of O2 use in IB can be used as a screening biomarker for the diagnosis of CFS. (AU)

Analysis of the injuries and workload evolution using the RPE and s-RPE method in basketball

The quantification of training loads provides valuable information to reduce overtraining and detecting the risk of injury. The present study looks into the evolution of the training load using the RPE and s-RPE method and describes the injuries observed. It is an observational study based on 9 subjects of the Pardinyes basketball team (Leb Plata category) who, in each practice and match, recorded their RPE. This value, together with the volume (in minutes), provides the s-RPE. All injuries and their typology were also recorded during the first round of the competition. A total of 124 sessions were registered and 14 injuries were described in the period that went from 09/19/2019 to 02/15/2020. The load evolution of each player has been compared to the team average and to the one perceived by the coach. The lower extremity was, by far, the most injured one (13/14 injury events). The highest percentage of injuries was registered during the last part of the training sessions and matches, coinciding with the highest physical and psychological fatigue, and 64% of them were due to microtrauma. These inexpensive and easy-to-use methods (RPE and s-RPE) provide valuable data for planning, in order to adjust loads and prevent overtraining and injuries. It is necessary to manage workload to provide the player with the ideal stimulus, minimizing the risk of injury and, at the same time, maximizing their performance.

Peptidoglycan Deacetylases in Bacterial Cell Wall Remodeling and Pathogenesis.

The bacterial cell wall peptidoglycan (PG) is a dynamic structure that is constantly synthesized, re-modeled and degraded during bacterial division and growth. Postsynthetic modifications modulate the action of endogenous autolysis during PG lysis and remodeling for growth and sporulation, but also they are a mechanism used by pathogenic bacteria to evade the host innate immune system. Modifications of the glycan backbone are limited to the C-2 amine and C-6 hydroxyl moieties of either GlcNAc or MurNAc residues. This paper reviews the functional roles and properties of peptidoglycan de-Nacetylases (distinct PG GlcNAc and MurNAc deacetylases) and recent progress through genetic studies and biochemical characterization to elucidate their mechanism of action, 3D structures, substrate specificities and biological functions. Since they are virulence factors in pathogenic bacteria, peptidoglycan deacetylases are potential targets for the design of novel antimicrobial agents.

Targeting transthyretin in Alzheimer's disease: Drug discovery of small-molecule chaperones as disease-modifying drug candidates for Alzheimer's disease.

Transthyretin (TTR) has a well-established role in neuroprotection in Alzheimer's Disease (AD). We have setup a drug discovery program of small-molecule compounds that act as chaperones enhancing TTR/Amyloid-beta peptide (Aß) interactions. A combination of computational drug repurposing approaches and in vitro biological assays have resulted in a set of molecules which were then screened with our in-house validated high-throughput screening ternary test. A prioritized list of chaperones was obtained and corroborated with ITC studies. Small-molecule chaperones have been discovered, among them our lead compound Iododiflunisal (IDIF), a molecule in the discovery phase; one investigational drug (luteolin); and 3 marketed drugs (sulindac, olsalazine and flufenamic), which could be directly repurposed or repositioned for clinical use. Not all TTR tetramer stabilizers behave as chaperones in vitro. These chemically diverse chaperones will be used for validating TTR as a target in vivo, and to select one repurposed drug as a candidate to enter clinical trials as AD disease-modifying drug.

Transglycosylation Activity of Engineered Bifidobacterium Lacto-N-Biosidase Mutants at Donor Subsites for Lacto-N-Tetraose Synthesis.

The health benefits of human milk oligosaccharides (HMOs) make them attractive targets as supplements for infant formula milks. However, HMO synthesis is still challenging and only two HMOs have been marketed. Engineering glycoside hydrolases into transglycosylases may provide biocatalytic routes to the synthesis of complex oligosaccharides. Lacto-N-biosidase from Bifidobacterium bifidum (LnbB) is a GH20 enzyme present in the gut microbiota of breast-fed infants that hydrolyzes lacto-N-tetraose (LNT), the core structure of the most abundant type I HMOs. Here we report a mutational study in the donor subsites of the substrate binding cleft with the aim of reducing hydrolytic activity and conferring transglycosylation activity for the synthesis of LNT from p-nitrophenyl ß-lacto-N-bioside and lactose. As compared with the wt enzyme with negligible transglycosylation activity, mutants with residual hydrolase activity within 0.05% to 1.6% of the wild-type enzyme result in transglycosylating enzymes with LNT yields in the range of 10-30%. Mutations of Trp394, located in subsite -1 next to the catalytic residues, have a large impact on the transglycosylation/hydrolysis ratio, with W394F being the best mutant as a biocatalyst producing LNT at 32% yield. It is the first reported transglycosylating LnbB enzyme variant, amenable to further engineering for practical enzymatic synthesis of LNT.

Indolyl Septanoside Synthesis for In Vivo Screening of Bacterial Septanoside Hydrolases.

Building-up and breaking-down of carbohydrates are processes common to all forms of life. Glycoside hydrolases are a broad class of enzymes that play a central role in the cleavage of glycosidic bonds, which is fundamental to carbohydrate degradation. The large majority of substrates are five- and six-membered ring glycosides. Our interest in seven-membered ring septanose sugars has inspired the development of a way to search for septanoside hydrolase activity. Described here is a strategy for the discovery of septanoside hydrolases that uses synthetic indolyl septanosides as chromogenic substrates. Access to these tool compounds was enabled by a route where septanosyl halides act as glycosyl donors for the synthesis of the indolyl septanosides. The screening strategy leverages the known dimerization of 3-hydroxy-indoles to make colored dyes, as occurs when the ß-galactosidase substrate X-Gal is hydrolyzed. Because screens in bacterial cells would enable searches in organisms that utilize heptoses or from metagenomics libraries, we also demonstrate that septanosides are capable of entering E. coli cells through the use of a BODIPY-labeled septanoside. The modularity of the indolyl septanoside synthesis should allow the screening of a variety of substrates that mimic natural structures via this general approach.

Carbohydrate de-N-acetylases acting on structural polysaccharides and glycoconjugates.

Deacetylation of N-acetylhexosamine residues in structural polysaccharides and glycoconjugates is catalyzed by different families of carbohydrate esterases that, despite different structural folds, share a common metal-assisted acid/base mechanism with the metal cation coordinated with a conserved Asp-His-His triad. These enzymes serve diverse biological functions in the modification of cell-surface polysaccharides in bacteria and fungi as well as in the metabolism of hexosamines in the biosynthesis of cellular glycoconjugates. Focusing on carbohydrate de-N-acetylases, this article summarizes the background of the different families from a structural and functional viewpoint and covers advances in the characterization of novel enzymes over the last 2-3 years. Current research is addressed to the identification of new deacetylases and unravel their biological functions as they are candidate targets for the design of antimicrobials against pathogenic bacteria and fungi. Likewise, some families are also used as biocatalysts for the production of defined glycostructures with diverse applications.

Auxiliary active site mutations enhance the glycosynthase activity of a GH18 chitinase for polymerization of chitooligosaccharides.

Depolymerization of chitin results in chitooligosaccharides (COS) that induce immunostimulatory effects and disease protective responses and have many potential applications in agriculture and medicine. Isolation of bioactive COS with degree of polymerization (DP) larger than six from chitin hydrolyzates is hampered by their water insolubility. Enzymatic synthesis by exploiting the transglycosylation activity of GH18 chitinases offers a potential strategy to access oligomers in the range of bioactive DPs. We engineered SpChiD chitinase as a glycosynthase by mutation of the assisting residue of the catalytic triad in the substrate-assisted mechanism for polymerization of an oxazoline substrate (DP5ox). The insoluble polymer containing DP10 was partially hydrolyzed due to the significant residual hydrolase activity of the mutant enzyme. Combined mutations that strongly reduce the hydrolytic activity, in which the original catalytic triad only retains the essential acid/base residue, together with neighboring mutations in the -1/+1 subsites region, render glycosynthase-like chitinases able to produce chitin oligomers with DP10 as major product in good yields.

Preparative Scale Production of Recombinant Human Transthyretin for Biophysical Studies of Protein-Ligand and Protein-Protein Interactions.

Human transthyretin (hTTR), a serum protein with a main role in transporting thyroid hormones and retinol through binding to the retinol-binding protein, is an amyloidogenic protein involved in familial amyloidotic polyneuropathy (FAP), familial amyloidotic cardiomyopathy, and central nervous system selective amyloidosis. hTTR also has a neuroprotective role in Alzheimer disease, being the major Aß binding protein in human cerebrospinal fluid (CSF) that prevents amyloid-ß (Aß) aggregation with consequent abrogation of toxicity. Here we report an optimized preparative expression and purification protocol of hTTR (wt and amyloidogenic mutants) for in vitro screening assays of TTR ligands acting as amyloidogenesis inhibitors or acting as molecular chaperones to enhance the TTR:Aß interaction. Preparative yields were up to 660 mg of homogenous protein per L of culture in fed-batch bioreactor. The recombinant wt protein is mainly unmodified at Cys10, the single cysteine in the protein sequence, whereas the highly amyloidogenic Y78F variant renders mainly the S-glutathionated form, which has essentially the same amyloidogenic behavior than the reduced protein with free Cys10. The TTR production protocol has shown inter-batch reproducibility of expression and protein quality for in vitro screening assays.

Plasmodium falciparum Apicomplexan-Specific Glucosamine-6-Phosphate N-Acetyltransferase Is Key for Amino Sugar Metabolism and Asexual Blood Stage Development.

UDP-N-acetylglucosamine (UDP-GlcNAc), the main product of the hexosamine biosynthetic pathway, is an important metabolite in protozoan parasites since its sugar moiety is incorporated into glycosylphosphatidylinositol (GPI) glycolipids and N- and O-linked glycans. Apicomplexan parasites have a hexosamine pathway comparable to other eukaryotic organisms, with the exception of the glucosamine-phosphate N-acetyltransferase (GNA1) enzymatic step that has an independent evolutionary origin and significant differences from nonapicomplexan GNA1s. By using conditional genetic engineering, we demonstrate the requirement of GNA1 for the generation of a pool of UDP-GlcNAc and for the development of intraerythrocytic asexual Plasmodium falciparum parasites. Furthermore, we present the 1.95 Å resolution structure of the GNA1 ortholog from Cryptosporidium parvum, an apicomplexan parasite which is a leading cause of diarrhea in developing countries, as a surrogate for P. falciparum GNA1. The in-depth analysis of the crystal shows the presence of specific residues relevant for GNA1 enzymatic activity that are further investigated by the creation of site-specific mutants. The experiments reveal distinct features in apicomplexan GNA1 enzymes that could be exploitable for the generation of selective inhibitors against these parasites, by targeting the hexosamine pathway. This work underscores the potential of apicomplexan GNA1 as a drug target against malaria.IMPORTANCE Apicomplexan parasites cause a major burden on global health and economy. The absence of treatments, the emergence of resistances against available therapies, and the parasite's ability to manipulate host cells and evade immune systems highlight the urgent need to characterize new drug targets to treat infections caused by these parasites. We demonstrate that glucosamine-6-phosphate N-acetyltransferase (GNA1), required for the biosynthesis of UDP-N-acetylglucosamine (UDP-GlcNAc), is essential for P. falciparum asexual blood stage development and that the disruption of the gene encoding this enzyme quickly causes the death of the parasite within a life cycle. The high-resolution crystal structure of the GNA1 ortholog from the apicomplexan parasite C. parvum, used here as a surrogate, highlights significant differences from human GNA1. These divergences can be exploited for the design of specific inhibitors against the malaria parasite.