Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

Migration of canine neutrophils to chitin and chitosan.

Abstract: Suspension of chitin and chitosan particles (mean size of 1 micron) were found to attract canine neutrophils chemotactically as determined by a checkerboard assay through polycarbonate filter with 5 microns pore size in Blind well chamber. Suspension of chitin induced chemokinetic migrations of the neutrophils. These evidences might reflect accumulation of neutrophils to chitin- and chitosan-implanted regions in dogs.

Characterization of an Exo-β-d-Glucosaminidase Involved in a Novel Chitinolytic Pathway from the Hyperthermophilic Archaeon Thermococcus kodakaraensis KOD1

Abstract: Chitin, an insoluble β-1,4-linked linear polymer of N-acetylglucosamine (GlcNAc), is the second most abundant organic compound on our planet after cellulose. Previously known biodegradation pathways of chitin are summarized in Fig. ​Fig.1A.1A. It is degraded into dimer units of GlcNAc (GlcNAc2) by the combination of endo- and exo-type chitinases (reactions 1 and 2). β-N-Acetylglucosaminidase (GlcNAcase; reaction 3) further hydrolyzes the dimer to form GlcNAc or releases GlcNAc from chitooligosaccharides (6). Some organisms degrade GlcNAc2 to GlcNAc and GlcNAc-1-phosphate by GlcNAc2 phosphorylase (reaction 4) (28) or convert the dimer to GlcNAc-6-phosphate-GlcNAc by a GlcNAc2 phosphotransferase system (reaction 5) followed by degradation to GlcNAc and GlcNAc-6-phosphate by 6-phospho-β-glucosaminidase (reaction 6) (15, 16). Another pathway for chitin degradation is proposed to occur through deacetylation of chitin by chitin deacetylase (reaction 7). The resulting deacetylated chitin, chitosan, is then degraded to glucosamine (GlcN) by chitosanase (endo-type enzyme [reaction 8]) in cooperation with exo-β-d-glucosaminidase (GlcNase; reaction 9) (6). In contrast to the many studies on chitinases, chitosanases, GlcNAcases, and chitin deacetylases, information concerning GlcNase has been quite limited (20, 22, 25, 36). Moreover, a gene encoding GlcNase has not yet been cloned from any source. FIG. 1. (A) Previously known chitin catabolic pathways from chitin to monosaccharides. Enzymes are displayed as 1, endochitinase; 2, exochitinase; 3, GlcNAcase; 4, GlcNAc2 phosphorylase; 5, GlcNAc2 phosphotransferase system; 6, 6-phospho-β-d-glucosaminidase; ... We previously reported the first cloning and characterization of chitinase from an archaeon (32, 33). The chitinase from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 (previously reported as Pyrococcus kodakaraensis KOD1) possesses endo- and exo-type catalytic domains together with three chitin-binding domains on a single polypeptide. It has also been clarified that this chitinase (ChiATk) produces GlcNAc2 as an end product from chitin. However, the fate of GlcNAc2 in T. kodakaraensis remained to be solved. Interestingly, no gene homologous to any of the known GlcNAc2-processing enzymes (GlcNAcase, GlcNAc2 phosphorylase, and GlcNAc2 phosphotransferase system) could be identified in the preliminary complete genome sequence of strain KOD1. This is also the case for other archaeal genomes, including those of Pyrococcus furiosus and Halobacterium sp. strain NRC-1, both of which possess putative chitinase genes (3, 24). These facts suggested the existence of a novel type of enzyme or an unknown chitinolytic pathway in Archaea. This study aimed to identify the enzymes involved in the downstream steps of chitinolysis after chitinase in T. kodakaraensis KOD1. Through a search of the T. kodakaraensis genome, we found a gene initially identified as a putative β-glycosyl hydrolase located near the chitinase gene and demonstrated that the gene product was a GlcNase. As a GlcNase gene has not yet been identified from any organism, including Archaea, we report the characterization of this GlcNase (GlmATk) and contemplate its contribution to a novel GlcNAc2 degradation pathway in the archaeon T. kodakaraensis (Fig. ​(Fig.1B1B).

Studies on Chitin. I. Acetylation of Chitin

Abstract: Chitin was converted into diacetylchitin and also into various kinds of acetylchitins. A fully acetylated chitin was prepared by the acetylation of chitin in acetic anhydride—methanesulfonic acid mixture at 0°C overnight, or in acetic anhydride—perchloric acid mixture at 0°C for 3 h. Variously acetylated chitins were prepared by similar procedures applying a calculated amount of acetic anhydride in glacial acetic acid. The reaction of alkaline chitin with acetic anhydride gave 0.3 acetylchitin (0.3 mol of –OH groups are acetylated per one N-acetylglucosamine residue), and heating this with anhydrous sodium acetate in acetic anhydride produced ca 1.1 acetylchitin. However, it was difficult to further improve the degree of acetylation by this alkaline method. The acetylation of chitin resulted in an increase of solubility in formic acid, and diacetylchitin was easily soluble even in 85-% aqueous formic acid. The analytical data showed that the chitin residue exists as a stable hemihydrate unless it is completely acetylated. Infrared absorption spectra for chitin and acetylchitins were also investigated.

Chitin-Silk Fibroin Interactions: Relevance to Calcium Carbonate Formation in Invertebrates

Abstract: In mineralized tissues chitin is almost always associated with proteins, many of which are known to have chitin recognition consensus sequences. It has been observed in some mollusk shells that there is a well-defined spatial relation between the crystallographic axes of the crystals and the chitin fibrils. This implies that the chitin functions directly or indirectly as a template for nucleation of the mineral phase. It is thus of much interest to understand the exact nature of the interface between the chitin and the proteins at the molecular level in mineralized tissues. Chitin/silk fibroin interactions were studied in vitro at the molecular level using homogenous films composed of the two macromolecules. The results show that the silk fibroin intercalates between the molecular planes of the chitin, and that the interactions are mainly through the chitin acetyl groups. Published X-ray diffraction patterns and infrared spectra of mineralized tissue organic matrices, as well as infrared spectra reported here of the squid pen and lobster cuticle, all show that in vivo the chitin and protein are not intimately mixed, but exist as two phases. We deduce that there is an interfacial plane between them in which the interactions are through the amide groups.