Showing papers on "Chitin published in 1976"

Studies on chitin, 2. Effect of deacetylation on solubility

Abstract: A reproducible method for obtaining water-soluble chitin and a relationship between solubility and degree of deacetylation of chitin were studied. It was found that the regenerated chitin isolated at low temperature from an alkali chitin solution left at 25°C for 48 to 77h showed very good solubility in water at 0°C. The degree of deacetylation of an alkaline treated chitin was determined by titration with hydrochloric acid. It increased rapidly to about 75% as the alkaline treatment time increased and began to level off to about 90% and only the regenerated chitin samples with around 50% of deacetylation were found to be soluble in water. The X-ray diffraction diagrams showed that these were amorphous, although both chitin with lower degree of deacetylation and chitosan had crystallinity. The improved solubility of chitin with about 50% of deacetylation would be attributed to the partial deacetylation which probably brought about the destruction of secondary structure and also the increase of the hydrophilic property on account of the increased number of amino groups.

Proteolytic activation and inactivation of chitin synthetase from Mucor rouxii.

Abstract: Summary: Crude chitin synthetase preparations from the mycelial and yeast forms of Mucor rouxii behaved differently. The mycelial preparations, incubated at 28 °C, lost virtually all chitin synthetase activity in a few hours; by contrast, the activity of enzyme preparations from yeast cells increased several fold during similar incubations. These spontaneous changes were probably caused by endogenous protease(s). Seemingly, the chitin synthetase in yeast preparations was present mainly in a latent, ‘zymogenic’, form that was activated by proteases. In the mycelial preparations, chitin synthetase was present mainly in an active state and was rapidly degraded by endogenous proteolysis. Exogenous proteases accelerated activation and destruction of chitin synthetase; an acid protease from Rhizopus chinensis was the most effective activator. The activation of chitin synthetase was inhibited by a soluble protein in the cell-free extract. Treatment with the detergent Brij 36T stabilized the chitin synthetase of crude preparations against spontaneous changes. Stabilized preparations were rapidly activated by exogenous proteases. The different behaviour of chitin synthetases in crude extracts of mycelium and yeast cells is consistent with, and perhaps partially responsible for, the differences in wall construction between mycelial and yeast forms of M. rouxii.

Lysozyme and chitinase in blood and lymphomyeloid tissues of marine fish

Abstract: The enzyme lysozyme (muramidase) has a degrading effect on chitin, but chitinase is more effective in this respect Both enzymes occur in fish, but their distribution and function are poorly known Activities of lysozyme and chitinase were measured in body fluids and tissues of marine fish Lysozyme was estimated by a plate method, chitinase by a viscosimetric method with glycol chitin as substrate pH optima and other characteristics were studied Lysozyme was found in lymphomyeloid (haematopoietic) tissues of chondrichtyan fish (rays, shark, Chimaera monstrosa) and in the plasma and lymph of certain teleosts Chitinase occurred in lymphomyeloid tissues (except thymus) of chondrichthyans and teleosts, and in the plasma and lymph of teleosts The results indicate that these enzymes are normal components of fish blood Probably they are produced by the granulocytes, white blood corpuscles rich in lysosomes The enzymes might have defence functions in fish blood Lysozyme is bacteriolytically active while chitinase possibly offers protection against chitincontaining parasites Very high chitinase activity was found in the pancreas of C monstrosa The pancreatic enzyme probably has a digestive function

On the nature and formation of the fibrillar nets produced by protoplasts of Saccharomyces cerevisiae in liquid media: an electronmicroscopic, X-ray diffraction and chemical study.

Abstract: SUMMARY: The nets produced by protoplasts of Saccharomyces cerevisiae in liquid culture media consisted of microfibrils about 20 nm wide, forming flat, fairly straight bundles of variable width and length, up to about 500 nm wide and 4 μm long. Ends of microfibrils were seldom found. They were not attacked by chitinase or dilute acids, but the net structure disappeared in 3% (w/v) NaOH, leaving about 60% dry wt of the nets as partly microfibrillar clusters. The X-ray powder pattern from the nets, in contrast to that from normal walls, exhibited a set of well-defined rings which identified two micro-crystalline constituents: chitin and unbranched chains of β-(I → 3)-linked D-glucose residues. These latter were the alkali-soluble fraction. The X-ray diagram of the glucan, corresponding to that of paramylon, indicated an in vivo crystal modification. Up to 15% dry wt was chitin which was formed de novo by the protoplasts. A fine net structure of microfibrils about 7·5 to 10 nm thick with meshes about 20 to 60 nm wide was demonstrated in normal walls, forming the entire inner layer and consisting mainly of yeast glucan. This glucan and chitin were only slightly crystalline in these walls. The features of the glucan and chitin of the protoplast nets indicate that enzymes active in normal wall formation were differentially removed or inactivated by the liquid medium.

Chitinase production by an Arthrobacter sp. lysing cells of Fusarium roseum

Abstract: An Arthrobacter sp. which actively lysed Fusarium roseum was found to liberate chitinase (E.C. 3.2-1.14, chitin glycanohydrolase), an enzyme essential for the hydrolysis of chitin, a major component of fusarial hyphal walls. Factors involved in the production of chitinase were investigated by modifying culture conditions and assaying for enzyme activity. Production occurred on colloidal chitin as well as on native chitin supplemented with yeast extract or peptone. Enzyme production paralleled growth; liberation of enzyme took place during the log phase with the maximum yield being obtained at the stationary phase. Addition of the non-ionic surfactant, polyoxyethylene sorbitan monooleate (Tween 80) increased enzyme yield. An inverse relationship was found between the amount of enzyme produced and the quantity of n-acetyl-glucosamine liberated. The enzyme was generally not produced when grown on various other carbohydrates. These findings suggest that chitinase is inducible and that chitin breakdown is regulated by a repressor-inducer mechanism. Initial hydrolysis rates of colloidal chitin were proportional to the concentration of chitinase used. Optimal pH and temperature for enzyme activity were 4.9 and 50°C, respectively. Purification of the chitinase was obtained by (NH4)2SO4 precipitation followed by DEAE-cellulose and Sephadex chromatography, achieving a 12-fold increase in specific activity.

Synthesis of chitin by particulate preparations from Aspergillus flavus

Abstract: 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 20mm. Chitin synthetase was competitively inhibited by polyoxin D (Ki 6.5 μm) and UDP (Ki 1.35mm), the latter giving complex kinetics.

Chitin biosynthesis during Blastocladiella zoospore germination: evidence that the hexosamine biosynthetic pathway is post-translationally activated during cell differentiation

Abstract: De novo construction of a chitinous cell wall accompanies Blastocladiella emersonii zoospore germination. At least an order of magnitude increase in total hexosamine occurs during germination. This increase is into polymer (chitin) and occurs on schedule in the presence of cycloheximide. Uridine-5'-diphospho-N-acetylglucosamine (UDPGlcNAc), both the end product of hexosamine biosynthesis and a substrate for chitin biosynthesis, is a potent inhibitor of the activity of the first pathway-specific enzyme of hexosamine biosynthesis in zoospore extracts. Certain uridine nucleotides, not perceptibly influencing the activity of the first enzyme per se, counteract the inhibitory effects of UDPGlcNAc. The concentration of UDPGlcNAc in the zoospore is sufficient to act as an inhibitor of the enzyme, but the amount of UDPGlcNAc is sufficient, by over an order of magnitude, to account for the chitin synthesized during germination. Both the production of UDPGlcNAc and its utilization for chitin synthesis appear to be post-translationally regulated in zoospores and during zoospore germination.

Some chemical and structural features of the conidial wall of Trichoderma viride

Abstract: Cell wall of spores of Trichoderma viride contains polymers similar to those of mycelial cell wall, such as β-(1 → 3), β-(1 → 6)glucans and protein, but chitin, always present in the mycelium, cannot be found in spores. Melanin, which in other fungi appears associated with chitin, replaces this polymer in the spore wall of T. viride and is located in the outermost layer. Attempts to characterize the pigment of the spore wall indicate that it is a non-indolic melanin-like polyphenol.

Chitinase of Bacillus thuringiensis

Abstract: Strains of Bacillus thuringiensis were shown to hydrolyse various forms of chitin around growing colonies on a solid medium. In conditions of submerged cultivation on a medium containing demineralized crab shells, Bac. thuringiensis var. caucasicus INMI Arm. 837 manifests the chitinolytic activity at the beginning of the stationary growth phase. The activity of chitinase which is of a constitutive nature increases when the bacterium is cultivated at pH 7.2. The maximum rate of hydrolysis of colloid chitin by chitinase prepared from the cultural broth is displayed at pH 8.0 and 60 degrees C.

Chitin synthesis in Triatoma infestans and other insects.

Abstract: In vivo and in vitro synthesis of chitin in Triatoma infestans was studied. For in vivo experiments, [14C] sugars were injected through the abdominal wall. Maximal incorporation of radioactivity into the cuticle was attained immediately after the ecdysis. The identification of in vivo synthesized chitin was performed by the enzymatic hydrolysis of the alkali-insoluble material from the cuticle with Helix chitinase. The main water-soluble compound obtained was N-acetylglucosamine as demonstrated by chromatographic procedures. In vitro synthesis of chitin was carried out with enzymatic crude extracts from Triatoma infestans, and UDP-N-acetylglucosamine was used as "source" of glycosyl moieties. Higher amounts of [14C] N-acetylglucosamine incorporation to chitin than those previously reported by others, were obtained. The identity of the product was confirmed in a similar way as that from in vivo synthesis. Radioactivity was also found in a liposoluble fraction concomitantly with chitin synthesis. This compound had an anionic behavior, was acid labile and had similar chromatographic properties as dolichol pyrophosphate N-acetylglucosamine obtained with pig liver extracts. Knowledge about dolichol phosphate sugars mediated glycoprotein synthesis in eukaryotes, suggests the involvement of this type of N-acetylglucosaminyl-phospholipid in macromolecule "building" even in insects.

[Chitinase from Serratia marcescens BKM B-851].

Abstract: The chitinase biosynthesis was studied during the cultivation of the strain of Serratia marcescens BKM B-851 with a high chitinolytic activity. Under submerged cultivation of bacterial cells on the medium containing demineralized crab shell extracellular chitinase showed maximum activity on the 3rd day. Cells of S. marcescens BKM B-851 synthesized chitinase as an adaptive enzyme. Chitinase obtained from the culture liquid by ammonium sulphate precipitation was then dialyzed and liophylized. It displayed optimum hydrolysis of colloid chitin at pH 7-8 and 50 degrees C and of native chitin at 30 degrees C.

Water-soluble, partially deacetylated chitin and its preparation

Abstract: PURPOSE: To obtain a water-soluble, partially deacetylated chitin usable as flocculants for water treatment, comprising 40-60% of N-acetyl-D-glucosamine and 60-40 % of D-glucosamine. COPYRIGHT: (C)1978,JPO&Japio

A process for purifying denatured chitin by reprecipitation

Abstract: PURPOSE:A process for renaturation and purification of denatured chitin by reprecipitating crude chitin obtained from a shell of an arthropod such as a robster, crab, etc.

Ultrastructural and Chemical Investigations on the Cell Wall Architecture of Epidermophyton Floccosum

Abstract: The chemical and ultrastructural architecture of the cell wall of Epidermophyton floccosum was investigated by extraction of the purified cell walls with alkali and/or acid, then by analysing the residues and extracts by gas liquid chromatography, X-ray diffraction and electron microscopy. The cell wall of E. floccosum appeared to be two layers: microfibrils and an amorphous matrix. The microfibrils as observed here are composed of chitin and a glucan in the core, and an alkali-insoluble, acidsoluble polysaccharide enveloping the chitin core. The amorphous matrix was also observed as a fine granular material, which is an alkali-soluble, 4 N-acetic acid-insoluble polysaccharide containing glucose, mannose and galactose. A schematic model of the cell wall is proposed and discussed.

Method for reclaiming a chitin from a degenerated chitin

Abstract: PURPOSE:A method for preparing a chitin having a completely homogeneous structure by acetylating amino grous in a partially deacetylated chitin.

Chemical Analysis for Chitin as a Measure of Fungal Infiltration of Cellulosic Materials

Abstract: An analytical chemical method is described to detect low-level fungus infiltration of cotton and jute by more rapid means than the conventional bacteriological techniques. Since chitin is present in the cell walls of most fungi, it was used as an indicator for fungal contamination. The amount of chitin found may serve as an indication of the degree of fungal contamination. For this purpose the quantitative analytical method for chitin determination by Rondle and Morgan was modified for the special requirements, and a technique was developed to eliminate the interference caused by the cellulosic-matrix. Data is presented which shows a good degree of correlation between the conventional bacteriological technique and the chemical.

Production of chitinase by Actinomyces kurssanovii and its properties

Abstract: Actinomyces kurssanovii, a culture producing large amounts of chitinase and chitobiase, was cultivated on a medium of the following composition (%): demineralized crab shells, 3.0; K2HPO4, 0.5; peptone, 0.2; yeast extract, 0.1; MgSO4-H2O, 0.09. The maximum amount of the enzymes was synthesized after growth in a fermenter of the actinomycete during 48 hours. The highest activity of chitinase is manifested at pH 7.0 and depends on ionic composition of the buffer, being higher in veronal buffer than in phosphate or tris//HC1 buffers. The chitinase and chitobiase of the strain decompose completely colloid chitin and chitin in demineralized crab shells with the formation of N-acetyl-D-glucosamine.