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At least 19 recordsLinked to original sources
PubMed2026

Cell wall-forming chitin synthases in a chytrid fungus.

Chitin is a critical structural component of fungal cell walls, yet our understanding of its synthesis across the kingdom Fungi remains limited. Here, we investigate chitin synthase diversity, transcription and localisation in the aquatic saprotrophic chytrid Rhizoclosmatium globosum, expanding insights into fungal cell wall biology beyond Dikaryan models. We identified 20 chitin synthase genes in the R. globosum genome, mostly canonical Division I and II types with conserved functional motifs. Transcriptomic analysis through zoospore, germling and immature thallus developmental stages revealed stage-specific expression patterns, with active gene diversity correlating with increasing morphological complexity. Using electroporation-based transformation and fluorescent fusion constructs, we indicate expression and localisation of two chitin synthases during cell development. Localisation patterns suggest dynamic redistribution from cytoplasmic dispersion in early encysted cells to concentrated signals at the sporangium wall. Expression in and around the apophysis indicates the importance of these structures in cell maintenance. Our findings highlight functional specialisation among chitin synthases and underscore the importance of cell wall integrity in chytrid development. This work establishes R. globosum as a genetically tractable model for studying chytrid cell biology and contributes to a broader understanding of fungal evolution and cell wall dynamics.

Biotechnology↗
PubMed1979

Chitin synthase activity from the slime variant of Neurospora crassa.

Chitin synthase (UDP-2-acetamido-2-deoxy-D-glucose:chitin 4-beta-acetamidodeoxy-D-glucosyltransferase, EC 2.4.1.16) activity from the wall-less variant of Neurospora crassa (slime) was partially characterized. The slime enzyme activity was found to be similar to that reported for slime-like and wild-type chitin synthase activities with respect to the following: specific activity, particulate cell-fraction localization, activation by N-acetylglucosamine, apparent Km with respect to substrate, pH optimum and ion requirement. It appears that the phenotype of slime cannot be solely accounted for by the absence of chitin synthase enzyme activity.

Acetylglucosamine↗
PubMed1975

Chitin synthase in Mortierella vinacea: properties, cellular location and synthesis in growing cultures.

Chitin synthase of Mortierella vinacea was present in the "microsomal' fraction (100 000 g precipitate), the 'cell-wall' fraction (2000 g precipitate) and the 'mitochondrial' fraction (10 000 g precipitate). The properties of the 'microsomal' enzyme were investigated. The pH optimum was between 5-8 and 6-2, and the temperature optimum was between 31 and 33 degrees C. The Km for UDP N-acetyl-D-glucosamine was 1.8 mM. The enzyme was stimulated by Mg2+ and a slight stimulation was also effected by N-acetyl-D-glucosamine. Soluble chitodextrins were inhibitory. A pH-dependent, heat-stable inhibitor of chitin synthase activity was present in the soluble cytoplasm from the mycelium. The effects of aeration and glucose concentration on enzyme production in growing cultures were also investigated; maximum specific activity of chitin synthase was associated with the cessation of exponential growth.

Acetylglucosamine↗
PubMed1979

Metabolic products of microorganisms. 181. Chitin synthase from fungi, a test model for substances with insecticidal properties.

Chitin synthase from Coprinus cinereus (Schaeff. ex Fr.) S. F. Gray (= C. lagopus sensu Buller) was used as a model for chitin synthase from insects. The effect of dimilin (difluorobenzuron), captan (trichloromethylsulfonyl fungicide), kitazin P (organophosphorus ester fungicide) and parathion (organophosphorus insecticide) on the fungal enzyme was compared with the effect of nikkomycin (nucleosidepeptide antibiotic).

Agaricales↗
PubMed1976

A particulate chitin synthase from Aspergillus flavus Link: the properties, location, and levels of activity in mycelium and regenerating protoplast preparations.

Chitin synthase (ED 2.4.1.16) has been characterized in Aspergillus flavus. A K(m) value of 2.5 m(M) was obtained for the substrate UDPGlcNAc. The enzyme had a requirement for GlcNAc, and Mg2+ and activity was increased in the presence of soluble chitodextrins F1 and F2. The optimum activity was obtained using Tris--HCl buffer, pH 7.5, with a secondary peak at pH 6.2 and an incubation temperature of 29.5 degrees C. Distribution patterns of chitin synthase in protoplasts and mycelial material were very similar. The highest specific activity was found in a 200 000 X g fraction. Enzyme levels in growing mycelium increased during the exponential growth phase after which they declined. Activity also increased during the early stages of regeneration of both conidial and mycelial protoplasts, despite an initial lack in net protein synthesis. Chitin synthase levels were also dependent upon the carbon source available during regeneration.

Aspergillus flavus↗
PubMed2026

Cryo-EM structures of Candida albicans chitin synthase Chs1 reveal a druggable translocation channel.

Invasive candidiasis is a leading cause of hospital-acquired bloodstream infections with high mortality. While the fungal cell wall is an excellent therapeutic target, inhibitor development against the essential chitin synthase (Chs) has been hampered by the absence of structural and mechanistic understanding of class II Chs, which contribute to fungal viability. Here we present cryo-electron microscopy structures of Candida albicans class II Chs (CaChs1) at 2.93-3.38 Å resolution, providing insights into its mechanisms of early elongation, chito-oligomer translocation and inhibition by the CaChs1-specific non-competitive inhibitor diynyl arylamine (DA). Chitin elongation and translocation are coupled to coordinated motion of the glycosyltransferase domain and the dimer interface. Notably, DA binds within the chitin translocation channel where a regulatory lipid resides and inhibits the enzyme by occluding product polymer extrusion. Importantly, DA showed potent synergy with the class I Chs inhibitor nikkomycin Z against C. albicans and Candida auris. These findings establish the chitin translocation channel as a druggable site for rational antifungal design.

Journal Article↗
PubMed1977

Chitin biosynthesis in protoplasts and subcellular fractions of Aspergillus fumigatus.

The biosynthesis of chitin has been obtained in broken mycelia and protoplasts of the fungus Aspergillus fumigatus. The specific activity of chitin synthase (EC 2.4.1.16) in a membrane preparation from protoplasts derived from the hyphal tips of A. fumigatus was 26.8-fold greater than that of the chitin synthase in broken mycelia, indicating that the active chitin synthase is located primarily in a membrane-bound site at the hyphal tip. Polyoxin D was a potent competitive inhibitor of the enzyme, having Ki 5.2 +/- 0.8 micron with respect to the natural substrate UDP-N-acetyl-D-glucosamine, which has Km 1.58 mM.

Anti-Bacterial Agents↗
PubMed2026

De novo transcriptome meta-analysis reveals candidate genes involved in life-stage transitions for RNAi-mediated management of the citrus root weevil (Diaprepes abbreviatus).

BACKGROUND: The citrus root weevil, Diaprepes abbreviatus, is a destructive agricultural pest for which molecular control options remain limited due to historically sparse genomic resources. Leveraging a comprehensive de novo transcriptome, we investigated developmental gene regulation across larval, pupal, and adult stages and identified essential targets for RNA interference (RNAi)-based intervention. RESULTS: Stage-resolved transcriptomic analyses revealed extensive transcriptional reprogramming associated with metabolism, detoxification, cuticle biosynthesis, endocrine signaling, and sensory perception. Among these, chitin synthase (DaCHS) emerged as a critical developmental gene, exhibiting pronounced up-regulation during late larval and pupal stages corresponding to intensive cuticle synthesis. Phylogenetic and structural analyses demonstrated that DaCHS is highly conserved among insects and retains canonical catalytic domains and transmembrane topology. Alpha Fold-based structural modeling and molecular docking confirmed stable interaction of DaCHS with its substrate, N-acetylglucosamine, supporting functional conservation of enzymatic activity. Oral delivery of DaCHS double-stranded RNA induced robust transcript suppression, leading to significant mortality and severe developmental defects, including larval and pupal abnormalities, and adults with disrupted wing and abdominal morphogenesis. CONCLUSION: These findings establish DaCHS as an indispensable gene for D. abbreviates development and validate transcriptome-guided RNAi as a powerful framework for target discovery. This work provides a strong molecular foundation for developing RNAi-based strategies that can be integrated into sustainable management programs for citrus root weevil control. © 2026 Society of Chemical Industry.

Animals↗
PubMed1979

Characteristics of the chitin-synthesizing system of insect tissue.

Results obtained from isotopic dilution experiments are consistent with the operation of the chitin pathway as it has been established in fungal preparations. The last enzyme in this pathway, namely chitin synthase, seems to be accessible to substrate from the cell exterior, indicating its presence in the plasma membrane. It can, however, only be saturated (in a manner that partially excludes reaction with a competing substrate) from the cell side of the membrane.

Acetylglucosamine↗
PubMed2026

Development of a Droplet-Based RNA Interference Feeding Assay for Neonates of the Citrus Root Weevil Diaprepes abbreviatus.

The citrus root weevil, Diaprepes abbreviatus, is an economically important pest of citrus and ornamental crops whose subterranean larval feeding damages roots and predisposes plants to secondary pathogen infection. Development of efficient RNA interference (RNAi) delivery methods for early larval stages is essential for functional genomics studies and the evaluation of RNAi-based pest management strategies. In this study, we developed a droplet-based feeding assay for oral delivery of double-stranded RNA (dsRNA) to neonates of D. abbreviatus using chitin synthase 2 (DaCHS2) as a model RNAi target to validate the assay. Feeding solutions containing dsRNA were supplemented with sucrose and bromophenol blue dye, with bromophenol blue used to visually confirm ingestion. Across three independent biological replicates, all neonates exposed to DaCHS2-dsRNA, GFP-dsRNA, and water control droplets were confirmed to have ingested the feeding solution (45/45 neonates per treatment; 100% feeding success). Oral delivery of dsRNA targeting DaCHS2 reduced transcript abundance and was associated with developmental abnormalities and mortality, including incomplete molting, abnormal pigmentation, cuticular deformities, defective pupation, and malformed adults. Regression analysis demonstrated moderate and significant relationship between dsRNA concentration and neonate mortality and developmental abnormalities. RT-qPCR further confirmed reduced DaCHS2 transcript abundance following oral dsRNA exposure. The developed assay provides a simple, reproducible, and minimally invasive proof-of-concept platform for oral dsRNA delivery to D. abbreviatus neonates. The assay requires only small dsRNA volumes, provides visual confirmation of ingestion, and may facilitate laboratory-based screening of additional RNAi target genes in D. abbreviatus and other coleopteran pests.

Animals↗
PubMed1979

Septum formation, cell division, and sporulation in mutants of yeast deficient in proteinase B.

Mutants of Saccharomyces cerevisiae that carry lesions in the structural gene for proteinase B, prb1, have been isolated. Proteinase B was thought to be involved in activation of chitin synthase zymogen to allow septum formation during budding and to be involved in sporulation. The prb1 mutants are able to grow and divide and they form apparently normal septa that contain chitin. Most diploids homozygous for prb1 mutations are unable to complete sporulation.

Alleles↗
PubMed1976

Synthesis of chitin by particulate preparations from Aspergillus flavus.

Cell-free extracts from Aspergillus flavus catalyzed the synthesis of chitin from UDP-GlcNAc. Most of the activity was associated with membrane-rich fractions whereas no activity was detected in the cell walls. Chitin synthetase was activated by fungal acid proteases; animal and plant proteases destroyed it. Upon incubation at 0 C and 28 C chitin synthetase was inactivated, probably by the action of proteases present in the particulate preparations. Maximal activity was obtained at pH 6.6-7.1 and 15 C. Arrhenius plot showed a biphasic curve with the transition at 7 C. E values were 3300 Kcal/mole above this temperature and 15500 Kcal/mole below it. The enzyme was activated by GlcNAc and required a divalent metal, the most active being Mg++. By plotting v vs UDP-GlcNAc concentration a sigmoidal curve was obtained. Km calculated at high substrate concentrations was 20 mM. Chitin synthetase was competitively inhibited by polyoxin D (Ki 6.5 muM) and (Ki 1.35 mM), the latter giving complex kinetics.

Anti-Bacterial Agents↗
PubMed1979

Studies on a proteinase B mutant of yeast.

Yeast mutant lacking proteinase B activity have been isolated [Wolf, D. H. and Ehmann, C. (1978) FEBS Lett. 92, 121--124]. One of these mutants (HP232) is characterized in detail. Absence of the vacuolar localized enzyme is confirmed by checking for proteinase B activity in isolated mutant vacuoles. Defective proteinase B activity segregates 2:2 in meiotic tetrads. The mutation is shown to be recessive. Mutant proteinase B activity is not only absent against the synthetic substrate. Azocoll, but also against the physiological substrate pre-chitin synthetase, cytoplasmic malate dehydrogenase and fructose-1,6-bisphosphatase. The mutant shows normal vegetative growth, a phenomenon not consistent with the idea that proteinase B might be the activating principle of chitin synthetase zymogen in vivo. Fluorescence microscopy shows normal chitin insertion. Enzymes underlying carbon-catabolite inactivation in wild-type cells (a mechanism proposed to be possibly triggered by proteinase B) such as cytoplasmic malate dehydrogenase, fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase and isocitrate lyase, are inactivated also in the mutant. NADP-dependent glutamate dehydrogenase, which is found to be inactivated in glucose-starved wild-type cells, proceeds normally in the mutant. Mutant cells show more than 40% reduced protein degradation under starvation conditions. Sporulating diploids, homozygous for proteinase B absence, also exhibit an approximately 40% reduced protein degradation as compared to homozygous wild-type diploids or diploids heterozygous for the mutant gene. The time of the appearance of the first ascospores of diploid cells, homozygous for proteinase B deficiency, is delayed about 50% and sporulation frequency is reduced to about the same extent as compared to homozygous wild-type diploids or diploids heterozygous for the mutant gene.

Chitin Synthase↗
PubMed1979

Chitin synthetase distribution on the yeast plasma membrane.

Purified, intact yeast plasma membranes were allowed to synthesize chitin, and the nascent chains of polysaccharide were observed either by the fluorescence produced with a brightener or by autoradiography. By both methods, it was concluded that the newly formed chitin emerged at many sites on each membrane. Thus, the synthetase that catalyzes chitin formation has a similar distribution. Since chitin synthetase is found mainly in a zymogen form, these results confirm the hypothesis that initiation of the chitinous primary septum of Saccharomyces occurs by localized activation of the uniformly distributed zymogen.

Cell Membrane↗
PubMed1978

Chitin synthesis in Candida albicans: comparison of yeast and hyphal forms.

Chitin synthesis was studied in both yeast and hyphae of the dimorphic fungus Candida albicans. Incorporation of N-acetyl-d-[1-(3)H]glucosamine ([(3)H]GluNAc) into an acid-alkali-insoluble fraction was 10 times greater in hyphal-phase cells. A crude preparation of chitin synthetase was obtained from sonically treated protoplasts of both forms of Candida. Enzyme activity, which was determined by using [(14)C]UDP-GLuNAc as a substrate, was exclusively associated with the 80,000 x g pellet from sonically treated protoplasts of both forms. It was determined that enzyme activity (nanomoles of [(14)C]UDP-GluNAc incorporated per milligram of protein) was approximately 2 times greater in hyphae versus yeast cells. Enzyme activity in both yeast and hyphae increased six- to sevenfold when the enzyme preparations were preincubated with trypsin. A vacuolar fraction, obtained from yeast cells but not from hyphae, stimulated enzyme activity when incubated with either yeast or hyphal enzyme preparations. Membrane fractions from protoplasts coated with [(3)H]concanavalin A before disruption were isolated by Renografin density gradient centrifugation. Chitin synthetase activity was preferentially associated with the concanavalin A-labeled fraction, suggesting that the enzyme was located on the plasma membrane. In addition, enzyme activity in protoplasts treated with cold glutaraldehyde before disruption was significantly greater than in protoplasts that were sonically disrupted and then treated with cold glutaraldehyde, indicating that the enzyme resides on the inner side of the plasma membrane.

Candida albicans↗
PubMed1979

Regulation and solubilization of Candida albicans chitin synthetase.

A cytoplasmic component which inhibited the activation of chitin synthetase was studied in the dimorphic fungus Candida albicans. The inhibitor was found to be heat stable and trypsin sensitive and was only effective when incubated with a vacuolar protease, an activator of chitin synthetase, before the activation of chitin synthetase. In addition, the particulate chitin synthetase from the yeast form of C. albicans was solubilized by a sodium cholate-digitonin extraction and subsequently was purified approximately 30-fold by Sepharose column chromatography and Amicon XM 100 filtration. Activity of the soluble enzyme was increased by the addition of trypsin or phosphatidyl serine. The molecular weight of the enzyme was estimated to be 400,000.

Candida albicans↗
PubMed1977

Properties of chitin synthetase in isolated chitosomes from yeast cells of Mucor rouxii.

Chitin synthetase was isolated and purified 120-fold from the supernatant fraction (54,500 X g) of broken yeast cells of Mucor rouxii. The purified preparations consisted mainly of chitin synthetase particles (chitosomes) with an average size larger than 7 X 10(6) daltons (by gel filtration) and an average sedimentation coefficient of 105 S. The samples also contained other enzyme complexes (fatty acid synthetase, pyruvate dehydrogenase, and, depending on method, ribosomes). Nearly all of the chitosomal chitin synthetase occurred in a zymogenic form that required proteolytic activation. In most properties, the chitosomal enzyme was similar to crude enzyme (54,000 X g sediment): kinetics, activation by proteases, response to metals, stimulation by N-acetylglucosamine, and inhibition by polyoxin or UDP. One mamor difference was the much greater stability of the chitosomal chitin synthetase zymogen against spontaneous activation and destruction. Product (chitin microfibril) and enzyme (chitin synthetase) remained associated in a complex that was readily separated by centrifugation.

Acetylglucosamine↗