Chitinase

About: Chitinase is a research topic. Over the lifetime, 4690 publications have been published within this topic receiving 161786 citations. The topic is also known as: 1,4-beta-poly-N-acetylglucosaminidase & poly-beta-glucosaminidase.

Analysis of subgroup C of fungal chitinases containing chitin-binding and LysM modules in the mycoparasite Trichoderma atroviride

Abstract: Fungi have a plethora of chitinases, which can be phylogenetically divided into three subgroups (A, B and C). Subgroup C (sgC) chitinases are especially interesting due to their multiple carbohydrate-binding modules, but they have not been investigated in detail yet. In this study, we analyzed sgC chitinases in the mycoparasites Trichoderma atroviride and Trichoderma virens. The expression of sgC chitinase genes in T. atroviride was induced during mycoparasitism of the fungal prey Botrytis cinerea, but not Rhizoctonia solani and correspondingly only by fungal cell walls of the former. Interestingly, only few sgC chitinase genes were inducible by chitin, suggesting that non-chitinous cell wall components can act as inducers. In contrast, the transcriptional profile of the most abundantly expressed sgC chitinase gene tac6 indicated a role of the protein in hyphal network formation. This shows that sgC chitinases have diverse functions and are not only involved in the mycoparasitic attack. However, sequence analysis and 3D modelling revealed that TAC6 and also its ortholog in T. virens have potentially detrimental deletions in the substrate-binding site and are thus probably not catalytically active enzymes. Genomic analysis showed that the genes neighboring sgC chitinases often encode proteins that are solely composed of multiple LysM modules, which were induced by similar stimuli as their neighboring sgC chitinase genes. This study provides first insights into fungal sgC chitinases and their associated LysM proteins.

Crystal structure and enzymatic properties of a bacterial family 19 chitinase reveal differences from plant enzymes

Abstract: We describe the cloning, overexpression, purification, characterization and crystal structure of chitinase G, a single-domain family 19 chitinase from the Gram-positive bacterium Streptomyces coelicolor A3(2). Although chitinase G was not capable of releasing 4-methylumbelliferyl from artificial chitooligosaccharide substrates, it was capable of degrading longer chitooligosaccharides at rates similar to those observed for other chitinases. The enzyme was also capable of degrading a colored colloidal chitin substrate (carboxymethyl-chitin-remazol-brilliant violet) and a small, presumably amorphous, subfraction of alpha-chitin and beta-chitin, but was not capable of degrading crystalline chitin completely. The crystal structures of chitinase G and a related Streptomyces chitinase, chitinase C [Kezuka Y, Ohishi M, Itoh Y, Watanabe J, Mitsutomi M, Watanabe T & Nonaka T (2006) J Mol Biol358, 472-484], showed that these bacterial family 19 chitinases lack several loops that extend the substrate-binding grooves in family 19 chitinases from plants. In accordance with these structural features, detailed analysis of the degradation of chitooligosaccharides by chitinase G showed that the enzyme has only four subsites (- 2 to + 2), as opposed to six (- 3 to + 3) for plant enzymes. The most prominent structural difference leading to reduced size of the substrate-binding groove is the deletion of a 13-residue loop between the two putatively catalytic glutamates. The importance of these two residues for catalysis was confirmed by a site-directed mutagenesis study.

Comparative Genomic Analysis of Chitinase and Chitinase-Like Genes in the African Malaria Mosquito (Anopheles gambiae)

Abstract: Chitinase is an important enzyme responsible for chitin metabolism in a wide range of organisms including bacteria, yeasts and other fungi, nematodes and arthropods. However, current knowledge on chitinolytic enzymes, especially their structures, functions and regulation is very limited. In this study we have identified 20 chitinase and chitinase-like genes in the African malaria mosquito, Anopheles gambiae, through genome-wide searching and transcript profiling. We assigned these genes into eight different chitinase groupings (groups I–VIII). Domain analysis of their predicted proteins showed that all contained at least one catalytic domain. However, only seven (AgCht4, AgCht5-1, AgCht6, AgCht7, AgCht8, AgCht10 and AgCht23) displayed one or more chitin-binding domains. Analyses of stage- and tissue-specific gene expression revealed that most of these genes were expressed in larval stages. However, AgCht8 was mainly expressed in the pupal and adult stages. AgCht2 and AgCht12 were specifically expressed in the foregut, whereas AgCht13 was only expressed in the midgut. The high diversity and complexity of An. gambiae chitinase and chitinase-like genes suggest their diverse functions during different developmental stages and in different tissues of the insect. A comparative genomic analysis of these genes along with those present in Drosophila melanogaster, Tribolium castaneum and several other insect species led to a uniform classification and nomenclature of these genes. Our investigation also provided important information for conducting future studies on the functions of chitinase and chitinase-like genes in this important malaria vector and other species of arthropods.

Tobacco Mesophyll Protoplasts Synthesize 1,3-β-Glucanase, Chitinases, and “Osmotins” during in Vitro Culture

Abstract: Tobacco ( Nicotiana tabacum ) mesophyll protoplasts synthesize six basic proteins (a, a′, a 1 , b, b′, and c) which are undetectable in the leaf and whose synthesis is reduced by auxin (Y Meyer, L Aspart, Y Chartier [1984] Plant Physiol 75: 1027-1033). Polypeptides a, a′, and a 1 were shown to have similar mobilities on two-dimensional electrophoresis as one 1,3-β-glucanase and two chitinases from tobacco mosaic virus-infected leaves. In immunoblotting experiments, polypeptide a was recognized by specific antibodies raised against the 1,3-β-glucanase and a′ and a 1 reacted with anti-chitinase antibodies. Similarly, b and b′ comigrated with osmotin and its neutral counterpart, two proteins characteristic of salt-adapted tobacco cells, and reacted with anti-osmotin antibodies. In addition it has been shown that 1,3-β-glucanase and chitinase activities increased at the same time as a, a′, and a 1 accumulated in cultivated protoplasts. Finally, polypeptide c was also detected in tobacco mosaic virus-infected leaves but could not be identified as any of the pathogenesis-related proteins characterized so far in tobacco. Thus, cultivated tobacco protoplasts synthesize and accumulate typical stress proteins.