Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chitin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed2006

Unique posttranslational modifications of chitin-binding lectins of Entamoeba invadens cyst walls.

Entamoeba histolytica, which causes amebic dysentery and liver abscesses, is spread via chitin-walled cysts. The most abundant protein in the cyst wall of Entamoeba invadens, a model for amebic encystation, is a lectin called EiJacob1. EiJacob1 has five tandemly arrayed, six-Cys chitin-binding domains separated by low-complexity Ser- and Thr-rich spacers. E. histolytica also has numerous predicted Jessie lectins and chitinases, which contain a single, N-terminal eight-Cys chitin-binding domain. We hypothesized that E. invadens cyst walls are composed entirely of proteins with six-Cys or eight-Cys chitin-binding domains and that some of these proteins contain sugars. E. invadens genomic sequences predicted seven Jacob lectins, five Jessie lectins, and three chitinases. Reverse transcription-PCR analysis showed that mRNAs encoding Jacobs, Jessies, and chitinases are increased during E. invadens encystation, while mass spectrometry showed that the cyst wall is composed of an approximately 30:70 mix of Jacob lectins (cross-linking proteins) and Jessie and chitinase lectins (possible enzymes). Three Jacob lectins were cleaved prior to Lys at conserved sites (e.g., TPSVDK) in the Ser- and Thr-rich spacers between chitin-binding domains. A model peptide was cleaved at the same site by papain and E. invadens Cys proteases, suggesting that the latter cleave Jacob lectins in vivo. Some Jacob lectins had O-phosphodiester-linked carbohydrates, which were one to seven hexoses long and had deoxysugars at reducing ends. We concluded that the major protein components of the E. invadens cyst wall all contain chitin-binding domains (chitinases, Jessie lectins, and Jacob lectins) and that the Jacob lectins are differentially modified by site-specific Cys proteases and O-phosphodiester-linked glycans.

Amino Acid Sequence↗
PubMed2000

The most abundant glycoprotein of amebic cyst walls (Jacob) is a lectin with five Cys-rich, chitin-binding domains.

The infectious stage of amebae is the chitin-walled cyst, which is resistant to stomach acids. In this study an extraordinarily abundant, encystation-specific glycoprotein (Jacob) was identified on two-dimensional protein gels of cyst walls purified from Entamoeba invadens. Jacob, which was acidic and had an apparent molecular mass of approximately 100 kDa, contained sugars that bound to concanavalin A and ricin. The jacob gene encoded a 45-kDa protein with a ladder-like series of five Cys-rich domains. These Cys-rich domains were reminiscent of but not homologous to the Cys-rich chitin-binding domains of insect chitinases and peritrophic matrix proteins that surround the food bolus in the insect gut. Jacob bound purified chitin and chitin remaining in sodium dodecyl sulfate-treated cyst walls. Conversely, the E. histolytica plasma membrane Gal/GalNAc lectin bound sugars of intact cyst walls and purified Jacob. In the presence of galactose, E. invadens formed wall-less cysts, which were quadranucleate and contained Jacob and chitinase (another encystation-specific protein) in secretory vesicles. A galactose lectin was found to be present on the surface of wall-less cysts, which phagocytosed bacteria and mucin-coated beads. These results suggest that the E. invadens cyst wall forms when the plasma membrane galactose lectin binds sugars on Jacob, which in turn binds chitin via its five chitin-binding domains.

Amino Acid Sequence↗
PubMed1981

Changes in the rate of chitin-plus-chitosan synthesis accompany morphogenesis of Mucor racemosus.

The in vivo differential rates of chitin-plus-chitosan biosynthesis in Mucor racemosus were determined under a variety of conditions, leading to yeast cell or mycelial morphology. Chitin-chitosan was determined as hot NaOH-insoluble radioactivity derived from N-acetyl-D-[1-3H]glucosamine in the medium. Control experiments demonstrated that the labeled material possessed the properties of chitin-plus-chitosan. Our results indicate that Mucor yeasts have a relatively low differential rate of chitin-plus-chitosan synthesis and that mycelial cells have a threefold-elevated differential rate. Treatment of aerobic cells with exogenous N6, O2-dibutyryl cyclic adenosine 3',5'-monophosphate, an agent which induces yeast cell morphology, also results in a lowered rate of chitin-plus-chitosan synthesis. Control experiments eliminated the possibility that the observed rate changes were due to changes in endogenous pool size, uptake of exogenous N-acetyl-p-[1-3H]glucosamine, or alterations in growth rate. Therefore, the changes are seemingly linked to morphogenesis. These results strengthen the idea that cyclic adenosine 3',5'-monophosphate plays an important role in dimorphism in Mucor. In addition, pulse-chase experiments suggest that considerable modification of newly synthesized chitin plus chitosan in both yeast cells and mycelia occurs in vivo.

Aerobiosis↗
PubMed1983

"Nonfibrillar" chitin associated with walls and septa of Trichophyton mentagrophytes arthrospores.

Two morphologically distinct forms of chitin were found in the arthrospore walls and septa of Trichophyton mentagrophytes. Two-thirds of the total wall chitin was the microfibrillar and chitinase-sensitive form. The remaining chitin existed in a previously uncharacterized "nonfibrillar" form and was insensitive to the action of Streptomyces chitinase. Exhaustive digestion of the arthrospore walls and septa with beta (1 leads to 3)-glucanase and chitinase followed by extraction with NaOH (1 N, 100 degrees C, 3 h) resulted in a fraction which retained the original wall shape. This fraction consisted of 85% N-acetylglucosamine, 2.0% galactosamine, 2.5% glucose, and 0.4% amino acids, 74% of which were lysine. Both its infrared spectrum and its X-ray diffraction pattern were almost identical to those of authentic chitin. There was no evidence of the presence of muramic acid, hexuronic acid, phosphate, or sulfate in this fraction. Its resistance to chitinase was due neither to the presence of protective wall layers or melanin nor to its close or covalent association with beta-glucan. Aside from its nonfibrillarity, this hexosamine polymer differed from authentic chitin in that it was soluble in 6 N HCl and 7.5 N NaOH. The development of this nonfibrillar chitin layer in the cell wall during arthrosporogenesis of T. mentagrophytes may be related to the arthrospores being resistant to a variety of antifungal agents.

Amino Acids↗
PubMed1992

Characterization of Aspergillus nidulans mutants deficient in cell wall chitin or glucan.

By screening for the osmotically remediable phenotype, mutations in two genes (orlA and orlB) affecting the cell wall chitin content of Aspergillus nidulans were identified. Strains carrying temperature-sensitive alleles of these genes produce conidia which swell excessively and lyse when germinated at restrictive temperatures. Growth under these conditions is remedied by osmotic stabilizers and by N-acetylglucosamine (GlcNAc). Remediation by GlcNAc suggests that the mutations affect early steps in the synthesis of chitin. Temperature and medium shift experiments indicate that the phenotype is the result of decreased synthesis rather than increased chitin degradation and that osmotic stabilizers act to stabilize a defective wall rather than to stabilize the gene product. Two genes, orlC and orlD, which affect cell wall beta-1,3-glucan content were also identified. Walls from strains carrying mutations in these genes exhibit normal amounts of alpha-1,3-glucan and chitin but reduced amounts of beta-1,3-glucan. As for the chitin-deficient mutants, orlC and orlD mutants spontaneously lyse on conventional media but are remedied by osmotic stabilizers. These results indicate that both chitin and beta-1,3-glucan are likely to contribute to the structural rigidity of the cell wall.

Aspergillus nidulans↗
PubMed1992

A study of embolizing materials for chemo-embolization therapy of hepatocellular carcinoma: embolic effect of cisplatin albumin microspheres using chitin and chitosan in dogs, and changes of cisplatin content in blood and tissue.

Hepatic artery of dogs was embolized with cisplatin (CDDP) albumin microspheres containing chitin and chitosan to investigate the in vivo CDDP release kinetics from CDDP albumin microspheres, the CDDP cumulative characteristics in the liver, and the influence of microsphere administration on hepatic tissue. Results showed that changes in blood CDDP content were dependent on CDDP albumin microsphere type and that release kinetics were better sustained when chitin was added to the microspheres or when the microspheres were treated with chitosan. In particular, the administration of CDDP in the chitin-containing CDDP chitosan albumin microspheres showed a blood CDDP content of approximately 0.26 micrograms Pt/ml 14 d after administration. The administration of chitin-containing or chitosan treated CDDP microspheres showed a CDDP content in the hepatic tissue of 0.14 to 0.23 micrograms Pt/g 28 d after administration. They also showed better control of CDDP release than those without chitin or chitosan treatment. No CDDP influence on hepatic tissue was observed. We conclude that, even in vivo, chitin and chitosan are effective embolic materials.

Animals↗
PubMed1975

[The chemistry of a chitin-protein from crayfish (Astacus fluviatilis) (author's transl)].

A chitin-protein complex is obtained from crayfish (Astacus fluviatilis) by gentle decalcification with acetic acid and EDTA. The complex is treated with lithium rhodanide, urea, anhydrous formic acid, pronase, papain, anhydrous formamide or 1N NaOH. The first three of these substances have little or no effect on the stability of the chitin-protein complex. The enzymes remove most of the protein, and the last two reagents remove all of it. The protein remaining bound to the polysaccharide after treatment of the chitin-protein complex with pronase or papain is relatively rich in glycine. Quantitative analysis yielded values for the acetyl, glucosaminyl and amino acid residues which reproduce the composition of the corresponding chitin-protein complex. In these calculations however, allowance must be made for the fact that glucosamine is partly destroyed by the acid by hydrolysis and interferes with the determination of basic amino acids. The results of the present work suggest that the chitin in crayfish is present in the form of a stable complex with protein, possibly held together by covalent binding of the protein to the chitin, with glycine as the connecting amino acid.

Amino Acids↗
PubMed2001

[The experimental study of intratemporal facial nerve regeneration in chitin chamber].

OBJECTIVE: To investigate the feasibility of intratemporal facial nerve regeneration in a chitin chamber. METHODS: A left 6 mm intratemporal facial nerve gap was created in adult white rabbit, and a total of 48 animals were used. The proximal and distal stumps were bridged with chitin chamber (experimental group) and silicone chamber (control group). Regeneration of the nerve was assessed by gross observation, nerve electrophysiological test, histological examination and digital morphological analysis in both groups. RESULTS: 1. Three months after implantation, the proximal transected neural stump was connected with the distal stump in the chitin chamber. Five months after operation, the regenerated nerve exhibited a more nature fascicular organization and the chitin tubes were completely absorbed. 2. Nerve evoked potentials showed better conduction ability in the chitin chamber. There were no significant difference in electrophysiological indices between the two chamber groups. 3. Most of the regenerated nerve fibers were myelinated nerve fibers, and axons and myelins had similar histograms between the experimental and control groups. 4. Five months after operation, the mean percentage of recovery of the regenerated nerve fiber area, axonal area and axonal number were more than 71% in the experimental group. There was no significant difference between the control and experimental groups. CONCLUSION: These results suggested that intratemporal facial nerve could regenerate effectively within the chitin chamber in rabbits and such kind of chamber may be clinically useful.

Animals↗
PubMedDate not supplied

[Isolation of chitin-specific wheat oxidoreductases].

Anionic peroxidase (IEP approximately 3.5) and oxalate oxidase (IEP approximately 7.0) were isolated from wheat seedlings using chitin. The strength of binding of enzymes with chitin depended on the degree of its acetylation and ionic strength of buffer. It was assumed that the acetyl groups of chitin are involved in sorption of enzymes on this biopolymer. The ability of anionic peroxidase and oxalate oxidase for sorption on chitin allows this biopolymer to be used for isolation of these proteins from plants. Cosorption of anionic peroxidase and oxalate oxidase on chitin suggests that these enzymes cooperate to ensure defensive response of wheat against chitin-containing pathogens.

Adsorption↗
PubMed1995

Molecular and genetic control of chitin biosynthesis in fungi.

Chitin is the most important structural component of the cell walls of fungi. Its synthesis involves the transfer of N-acetylglucosaminyl residues from the universal donor UDPGlcNAC to the growing chain. This reaction is catalyzed by an ill-defined enzyme called chitin synthetase. By use of diverse techniques, including reverse genetics, it has been possible to isolate mutants affected in chitin biosynthesis in vitro and in vivo. These studies have permitted the identification of several genes that code for the catalytic components of the enzyme, and probably for ancillary reactions. In general, two types of genes have been identified in fungi. The so-called CHS genes, from which two families, and possibly three classes exist, code for chitin synthetases activated by proteases. All fungi thus far studied contain more than one CHS gene, which are normally dispensable. The second class are larger, essential genes coding for the catalytic polypeptide of chitin synthetases non-activated by proteolysis, and probably made of more than one polypeptide. These are labeled CSD2 or CAL1. It may be hoped that our knowledge of chitin synthetase will make them the most suitable targets for new strategies to control fungal infections.

Amino Acid Sequence↗
PubMed1997

Chitin particle-induced cell-mediated immunity is inhibited by soluble mannan: mannose receptor-mediated phagocytosis initiates IL-12 production.

Previous studies showed that mouse spleen cells produced IL-12, TNF-alpha, and IFN-gamma when stimulated with phagocytosable-size chitin particles (N-acetyl-D-glucosamine polymers). To dissect the mechanisms of the cytokine production in this study, spleen cells from BALB/c mice were cultured with 1 to 10 microm chitin particles, heat-killed Corynebacterium parvum vaccine, zymosan, and mannan (a mannose polymer)-coated latex beads (1 microm) at 1, 10, or 100 microg/ml. We found that these particles induced IL-12, TNF-alpha, and IFN-gamma. However, these cytokines were not produced when spleen cells were cultured with soluble chitin, mannan, or laminarin (a polymer of beta-glucan), 1 to 10 microm beta-glucan particles, laminarin-coated latex beads, 1 microm latex beads, 50 to 100 microm chitin particles, or 50 to 100 microm mannan-coated beads. Soluble mannan, but not soluble laminarin, inhibited cytokine production following stimulation with 1 to 10 microm chitin particles, zymosan, or heat-killed C. parvum. In addition, cytochalasin D also inhibited cytokine production. The treatments with soluble mannan or with cytochalasin D, in sharp contrast, did not inhibit LPS-induced IL-12/IFN-gamma production or exogenous IL-12-induced IFN-gamma production. Finally, spleen cells from C3H/HeJ mice also showed comparable levels of IL-12/TNF-alpha/IFN-gamma production when induced by 1 to 10 microm chitin particles. Taken together, our results indicate that mannose receptor-mediated phagocytosis, but not the receptor-mediated pinocytosis, is highly associated with the production of IFN-gamma-inducing extracellular signaling factors such as IL-12 and TNF-alpha. The novel mechanism of phagocytosis-dependent IL-12 production appears to be distinct from that of LPS-induced cytokine production.

Actins↗
PubMed1992

Elicitation of Diterpene Biosynthesis in Rice (Oryza sativa L.) by Chitin.

Cell-free extracts of UV-irradiated rice (Oryza sativa L.) leaves have a much greater capacity for the synthesis from geranylgeranyl pyrophosphate of diterpene hydrocarbons, including the putative precursors of rice phytoalexins, than extracts of unstressed leaves (KA Wickham, CA West [1992] Arch Biochem Biophys 293: 320-332). An elicitor bioassay was developed on the basis of these observations in which 6-day-old rice cell suspension cultures were incubated for 40 hours with the substance to be tested, and an enzyme extract of the treated cells was assayed for its diterpene hydrocarbon synthesis activity as a measure of the response to elicitor. Four types of cell wall polysaccharides and oligosaccharide fragments that have elicitor activity for other plants were tested. Of these, polymeric chitin was the most active; a suspension concentration of approximately 7 micrograms per milliliter gave 50% of the maximum response in the bioassay. Chitosan and a branched beta-1,3-glucan fraction from Phytophthora megasperma f. sp. glycinea cell walls were only weakly active, and a mixture of oligogalacturonides was only slightly active. A crude mycelial cell wall preparation from the rice pathogen, Fusarium moniliforme, gave a response comparable to that of chitin, and this activity was sensitive to predigestion of the cell wall material with chitinase before the elicitor assay. N-Acetylglucosamine, chitobiose, chitotriose, and chitotetrose were inactive as elicitors, whereas a mixture of chitin fragments solubilized from insoluble chitin by partial acid hydrolysis was highly active. Constitutive chitinase activity was detected in the culture filtrate and enzyme extract of cells from a 6-day-old rice cell culture; the amount of chitinase activity increased markedly in both the culture filtrate and cell extracts after treatment of the culture with chitin. We propose on the basis of these results that soluble chitin fragments released from fungal cell walls through the action of constitutive rice chitinases serve as biotic elicitors of defense-related responses in rice.

Journal Article↗
PubMed2006

Synthesis and evaluation of a 99mTechnetium labeled chitin-binding protein as potential specific radioligand for the detection of fungal infections in mice.

AIM: Radiopharmaceuticals can be used to exploit differences between microorganisms in order to distinguish fungal from bacterial infection. Chitin, abundant in the cell wall of fungi, is not present in mammalian or bacterial cells and therefore represents a highly specific target to localize fungal infection. In this study, we have examined the potential of chitin-binding protein (CBP21) from Serratia marcescens as a specific radiotracer for the detection of invasive fungal infections. METHODS: CBP21 was labeled with 99mTc via hydrazinonicotinamide (HYNIC) and its characteristics were analyzed. In vitro binding studies with polymorphic chitin forms and microorganisms (fungi as well as bacteria) were performed. In vivo biodistribution of the compound was studied in immunocompromised mice with bacterial and fungal infections in the left and right thigh muscle, respectively, using 99mTc-HYNIC-myoglobin as size-matched control and 67Ga-citrate as positive control. Scintigraphic images were acquired at 1 and 7 h postinjection of the tracer. RESULTS: 99mTc-HYNIC-CBP21 was labeled with a radiochemical yield of 61% and a specific activity of 22.3 MBq/nmol. Highest in vitro binding percentages were found with beta-chitin (86.8+/-2.4%). Binding interactions to fungi were higher than to bacteria (P<0.05). In vivo, best ratios of fungal infection versus bacterial infection were seen at 5 and 7 h (3.6+/-1.2 and 2.9+/-1.4, respectively) postinjection of the tracer. Maximum uptake of the tracer in fungal infections (0.63+/-0.11%ID/g) at 7 h was significantly (P<0.05) higher than uptake seen in bacterial infections (0.34+/-0.11%ID/g) or the uptake of 99mTc-HYNIC-myoglobin (P<0.05) in the same infections (0.35+/-0.11%ID/g, respectively, 0.3+/-0.01%ID/g). CONCLUSIONS: This study shows that 99mTc-HYNIC-CBP21 is able to specifically interact with chitin in vitro. Scintigraphy and postmortem in vivo data indicate that 99mTc-HYNIC-CBP21 is able to distinguish fungal infection from bacterial infection probably due to a specific interaction of the protein with the chitin in the fungal cell wall.

Animals↗
PubMed1997

Lufenuron, a chitin-synthesis inhibitor, interrupts development of Drosophila melanogaster.

The chitin-synthesis inhibitor lufenuron was administered to Drosophila melanogaster to better understand the effects of chitin-synthesis interruption during the development and reproduction of this insect. When larvae were fed a diet containing a low concentration (< 1 ppm) of lufenuron, mortality was observed during either larval or pupal development, depending on the dose. Survivor adults were unable to fly, probably due to abnormal cuticular development in the wing hinge regions of the thorax. Larvae fed a higher concentration (10 ppm) completed development within that instar, but died during ecdysis to the next instar, presumably due to inadequate cuticle synthesis. Third instar larvae pupariated, but the puparium was abnormal, and pupation did not occur. Adults fed 10 ppm showed normal viability but slightly depressed oogenesis; additionally, although their eggs were fertilized, they failed to hatch. Examination of the embryos showed that they completed development but were unable to perforate the surrounding vitelline membrane, probably due to a weakened chitinous mouth hook assembly that was insufficiently rigid to effect hatching. These results identify stages during D. melanogaster development when chitin synthesis and deposition are critical. This information will be useful for identifying chitin-synthesis mutants of this insect.

Animals↗
PubMed2005

Analysis of chitin synthase function in a plant parasitic nematode, Meloidogyne artiellia, using RNAi.

A single chitin synthase gene is responsible for chitin production in the eggshells of the plant parasitic nematode Meloidogyne artiellia. In this paper we describe a functional analysis of this gene using RNAi as well as further analysis of two similar genes from the free-living nematode Caenorhabditis elegans. The parasitic life-style of M. artiellia required the development of a novel method for delivery of dsRNA to nematode eggs that may be of utility in other experimental systems. C. elegans chitin synthase genes were silenced by feeding nematodes bacteria expressing appropriate chitin synthase dsRNA from a plasmid vector, while M. artiellia egg masses were soaked in dsRNA solution. The results obtained demonstrated that the synthesis of chitin continues to take place in nematode eggs within the egg sac in the parasitic nematode, and that the removal of this activity affects egg development in both C. elegans and M. artiellia. The method described here provides a new way of investigating gene function in plant parasitic nematodes allowing the validity of potential target genes for novel control methods to be assessed. Furthermore, since intact egg cells within the gelatinous matrix of M. artiellia are permeable to dsRNA, eggs of other nematodes may also be similarly permeable to dsRNA and therefore amenable to use with dsRNAi.

Animals↗
PubMed2005

mummy/cystic encodes an enzyme required for chitin and glycan synthesis, involved in trachea, embryonic cuticle and CNS development--analysis of its role in Drosophila tracheal morphogenesis.

Tracheal and nervous system development are two model systems for the study of organogenesis in Drosophila. In two independent screens, we identified three alleles of a gene involved in tracheal, cuticle and CNS development. Here, we show that these alleles, and the previously identified cystic and mummy, all belong to the same complementation group. These are mutants of a gene encoding the UDP-N-acetylglucosamine diphosphorylase, an enzyme responsible for the production of UDP-N-acetylglucosamine, an important intermediate in chitin and glycan biosynthesis. cyst was originally singled out as a gene required for the regulation of tracheal tube diameter. We characterized the cyst/mmy tracheal phenotype and upon histological examination concluded that mmy mutant embryos lack chitin-containing structures, such as the procuticle at the epidermis and the taenidial folds in the tracheal lumen. While most of their tracheal morphogenesis defects can be attributed to the lack of chitin, when compared to krotzkopf verkehrt (kkv) chitin-synthase mutants, mmy mutants showed a stronger phenotype, suggesting that some of the mmy phenotypes, like the axon guidance defects, are chitin-independent. We discuss the implications of these new data in the mechanism of size control in the Drosophila trachea.

Amino Acid Sequence↗
PubMed2005

Synthesis of fluorescently labeled UDP-GlcNAc analogues and their evaluation as chitin synthase substrates.

[structure: see text] Chitin synthase (CS) polymerizes UDP-GlcNAc to form chitin (poly-beta(1,4)-GlcNAc), a key component of fungal cell wall biosynthesis. Little is known about the substrate specificity of chitin synthase or the scope of substrate modification the enzyme will tolerate. Following a previous report suggesting that 6-O-dansyl GlcNAc is biosynthetically incorporated into chitin, we became interested in developing an assay for CS activity based on incorporation of a fluorescent substrate. We describe the synthesis of two fluorescent UDP-GlcNAc analogues and their evaluation as chitin synthase substrates.

Chitin↗
PubMed1983

Integumental chitin synthase activity in cell-free extracts of larvae of the Australian sheep blowfly, Lucilia cuprina, and two other species of diptera.

Chitin synthase activity has been demonstrated in crude homogenates of larval integuments from L. cuprina and in similar preparations from Musca domestica and Calliphora erythrocephala. This is the first report of an insect integumental chitin synthase. This activity brings about the incorporation of radioactivity from UDP-N-acetyl-[14C]glucosamine into an ethanol- and alkali-insoluble form. A major part of this labelled product has been characterized as chitin by its insolubility in alkali, resistance to degradation by proteases and its susceptibility to digestion by chitinase and HCl. Most of the radioactivity solubilized during digestion by chitinase co-migrates with N-acetylglucosamine, glucosamine and chitobiose during paper chromatography. Some radioactivity also becomes incorporated into non-chitin products in this system. There is substantial evidence that incorporation is not brought about by whole epidermal cells or by microbial contamination in the homogenates. The extent of incorporation obtained with the homogenates is limited by the presence of degradative enzymes which rapidly break down the substrate (UDP-N-acetylglucosamine). The incorporation was partially inhibited (50-70%) by both polyoxin-D (apparent Ki 0.04 microM) and diflubenzuron (apparent Ki 5-8 microM). This is the first report of a cell-free chitin-synthesizing system derived from insect tissue which is sensitive to inhibition by diflubenzuron.

Acetylglucosamine↗