几丁质酶：修订间差异

几丁质生物包括许多细菌<ref name="pmid16332766">{{cite journal|title=Chitinase genes in lake sediments of Ardley Island, Antarctica||date=December 2005|journal=Applied and Environmental Microbiology|issue=12|doi=10.1128/AEM.71.12.7904-7909.2005|volume=71|pages=7904–9|pmc=1317360|pmid=16332766|vauthors=Xiao X, Yin X, Lin J, Sun L, You Z, Wang P, Wang F}}</ref>（例如[[气单胞菌目]]、[[芽孢桿菌属|芽孢杆菌属]]、[[弧菌属]]<ref name="pmid17933912">{{cite journal|title=Conservation of the chitin utilization pathway in the Vibrionaceae||date=January 2008|journal=Applied and Environmental Microbiology|issue=1|doi=10.1128/AEM.01412-07|volume=74|pages=44–51|pmc=2223224|pmid=17933912|vauthors=Hunt DE, Gevers D, Vahora NM, Polz MF}}</ref>等）。这些细菌具有[[病原体|致病性]]或者腐食性。它们入侵活的[[节肢动物]]、[[浮游动物]]或[[真菌]]，也可能会降解这些生物的残留物。

几丁质酶也存在于植物中（例如大麦种子中的几丁质酶：[[蛋白质资料库|PDB]]：1CNS），其中一些是致病性（PR）蛋白被诱导系统性获得抗性的一部分，表达则是由NPR1基因和[[水杨酸]]途径介导的，两者均涉及对真菌和昆虫的抵抗力。其他植物几丁质酶可能需要产生真菌共生酶。<ref name="pmid10875337">{{cite journal|title=Differential expression of eight chitinase genes in Medicago truncatula roots during mycorrhiza formation, nodulation, and pathogen infection|date=July 2000|journal=Molecular Plant-Microbe Interactions|issue=7|doi=10.1094/MPMI.2000.13.7.763|volume=13|pages=763–77|pmid=10875337|vauthors=Salzer P, Bonanomi A, Beyer K, Vögeli-Lange R, Aeschbacher RA, Lange J, Wiemken A, Kim D, Cook DR, Boller T|doi-access=free}}</ref>

尽管[[哺乳动物]]不产生几丁质，但它们具有两种功能性几丁质酶：壳三糖苷酶（CHIT1）和酸性哺乳动物几丁质酶（AMCase），以及具有高度序列相似性但缺乏几丁质酶活性的类似几丁质酶的蛋白质（例如YKL-40）。<ref>{{cite journal|title=Potential role of chitinase 3-like-1 in inflammation-associated carcinogenic changes of epithelial cells|date=November 2009|journal=World Journal of Gastroenterology|issue=42|doi=10.3748/wjg.15.5249|volume=15|pages=5249–59|pmc=2776850|pmid=19908331|vauthors=Eurich K, Segawa M, Toei-Shimizu S, Mizoguchi E}}</ref>

像纤维素一样，几丁质是一种相对耐降解的生物聚合物，<ref name="Akaki1">{{cite journal|title=Apparent chitin digestibilities in the Eastern screech owl (''Otus asio'') and the American kestrel (''Falco sparverius'')|journal=Journal of Experimental Zoology|issue=4–5|doi=10.1002/(SICI)1097-010X(19990301/01)283:4/5<387::AID-JEZ8>3.0.CO;2-W|year=2005|volume=283|pages=387–393|vauthors=Akaki C, Duke GE}}</ref>尽管某些鱼类能够消化几丁质，但通常不会被动物消化。<ref name="pmid15556391">{{cite journal|title=Digestive chitinolytic activity in marine fishes of Monterey Bay, California|date=November 2004|journal=Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology|issue=3|doi=10.1016/j.cbpb.2004.09.020|volume=139|pages=351–8|pmid=15556391|vauthors=Gutowska MA, Drazen JC, Robison BH|citeseerx=10.1.1.318.6544}}</ref>目前认为，动物的几丁质消化需要细菌共生体和长时间的发酵，类似于[[反刍动物]]的纤维素消化。然而，几丁质酶已经从包括人类在内的某些哺乳动物的胃中分离出来。<ref name="pmid17587796">{{cite journal|title=Human gastric juice contains chitinase that can degrade chitin|journal=Annals of Nutrition & Metabolism|issue=3|doi=10.1159/000104144|year=2007|volume=51|pages=244–51|pmid=17587796|vauthors=Paoletti MG, Norberto L, Damini R, Musumeci S}}</ref>

几丁质酶活性还可以在[[血液|人血]]<ref name="pmid7836450">{{cite journal|title=Purification and characterization of human chitotriosidase, a novel member of the chitinase family of proteins|date=February 1995|journal=The Journal of Biological Chemistry|issue=5|doi=10.1074/jbc.270.5.2198|volume=270|pages=2198–202|pmid=7836450|vauthors=Renkema GH, Boot RG, Muijsers AO, Donker-Koopman WE, Aerts JM|doi-access=free}}</ref><ref name="pmid7591134">{{cite journal|title=Chitinase activity in human serum and leukocytes|url=http://iai.asm.org/cgi/pmidlookup?view=long&pmid=7591134|date=December 1995|journal=Infection and Immunity|issue=12|doi=|volume=63|pages=4770–3|pmc=173683|pmid=7591134|vauthors=Escott GM, Adams DJ|access-date=2020-10-05|||}}</ref><ref name="pmid7591134" />和[[软骨]]<ref name="Hakala1">{{cite journal|title=Human cartilage gp-39, a major secretory product of articular chondrocytes and synovial cells, is a mammalian member of a chitinase protein family|date=December 1993|journal=The Journal of Biological Chemistry|issue=34|volume=268|pages=25803–10|pmid=8245017|vauthors=Hakala BE, White C, Recklies AD}}</ref>中检测到。与植物几丁质酶一样，这可能与病原体抗性有关。<ref name="pmid12071845">{{cite journal|title=The chitinase 3-like protein human cartilage glycoprotein 39 (HC-gp39) stimulates proliferation of human connective-tissue cells and activates both extracellular signal-regulated kinase- and protein kinase B-mediated signalling pathways|date=July 2002|journal=The Biochemical Journal|issue=Pt 1|doi=10.1042/BJ20020075|volume=365|pages=119–26|pmc=1222662|pmid=12071845|vauthors=Recklies AD, White C, Ling H}}</ref><ref name="Eijk1">{{cite journal|title=Characterization of human phagocyte-derived chitotriosidase, a component of innate immunity|date=November 2005|journal=[[International Immunology]]|issue=11|doi=10.1093/intimm/dxh328|volume=17|pages=1505–12|pmid=16214810|vauthors=van Eijk M, van Roomen CP, Renkema GH, Bussink AP, Andrews L, Blommaart EF, Sugar A, Verhoeven AJ, Boot RG, Aerts JM|doi-access=free}}</ref>

人体产生的几丁质酶（称为“人几丁质酶”）可能与[[过敏]]有关，[[哮喘]]与几丁质酶表达水平提高有关。<ref name="pmid16179638">{{cite journal|title=Polymorphisms and haplotypes of acid mammalian chitinase are associated with bronchial asthma|date=December 2005|journal=American Journal of Respiratory and Critical Care Medicine|issue=12|doi=10.1164/rccm.200506-890OC|volume=172|pages=1505–9|pmc=2718453|pmid=16179638|vauthors=Bierbaum S, Nickel R, Koch A, Lau S, Deichmann KA, Wahn U, Superti-Furga A, Heinzmann A}}</ref><ref name="pmid15996009">{{cite journal|title=Increased lungkine and chitinase levels in allergic airway inflammation: a proteomics approach|date=July 2005|journal=Proteomics|issue=11|doi=10.1002/pmic.200401169|volume=5|pages=2799–807|pmid=15996009|vauthors=Zhao J, Zhu H, Wong CH, Leung KY, Wong WS}}</ref><ref name="pmid16159614">{{cite journal|title=Chitinases and chitinase-like proteins in T(H)2 inflammation and asthma||date=September 2005|journal=The Journal of Allergy and Clinical Immunology|issue=3|doi=10.1016/j.jaci.2005.06.028|volume=116|pages=497–500|pmid=16159614|vauthors=Elias JA, Homer RJ, Hamid Q, Lee CG}}</ref><ref name="pmid15192232">{{cite journal|title=Acidic mammalian chitinase in asthmatic Th2 inflammation and IL-13 pathway activation|date=June 2004|journal=Science|issue=5677|doi=10.1126/science.1095336|volume=304|pages=1678–82|pmid=15192232|vauthors=Zhu Z, Zheng T, Homer RJ, Kim YK, Chen NY, Cohn L, Hamid Q, Elias JA}}</ref><ref name="chupp1">{{cite journal|title=A chitinase-like protein in the lung and circulation of patients with severe asthma|date=November 2007|journal=The New England Journal of Medicine|issue=20|doi=10.1056/NEJMoa073600|volume=357|pages=2016–27|pmid=18003958|vauthors=Chupp GL, Lee CG, Jarjour N, Shim YM, Holm CT, He S, Dziura JD, Reed J, Coyle AJ, Kiener P, Cullen M, Grandsaigne M, Dombret MC, Aubier M, Pretolani M, Elias JA}}</ref>

人类几丁质酶可以解释某些最常见的过敏（[[塵蟎科|尘螨]]，[[霉菌]][[孢子]]等都含有几丁质）和[[蠕虫]]（[[寄生虫]]）感染之间的联系，这是[[卫生学]]假说的一种形式<ref name="pmid16202576">{{cite journal|title=Infections and allergy - helminths, hygiene and host immune regulation|date=December 2005|journal=Current Opinion in Immunology|issue=6|doi=10.1016/j.coi.2005.09.001|volume=17|pages=656–61|pmid=16202576|vauthors=Maizels RM}}</ref><ref name="pmid14723608">{{cite journal|title=Review article: helminths as therapeutic agents for inflammatory bowel disease|date=January 2004|journal=Alimentary Pharmacology & Therapeutics|issue=2|doi=10.1111/j.0269-2813.2004.01803.x|volume=19|pages=167–77|pmid=14723608|vauthors=Hunter MM, McKay DM}}</ref><ref name="pmid12756068">{{cite journal|title=Causality or coincidence: may the slow disappearance of helminths be responsible for the imbalances in immune control mechanisms?|date=June 2003|journal=Journal of Helminthology|issue=2|doi=10.1079/JOH2003176|volume=77|pages=147–53|pmid=12756068|vauthors=Palmas C, Gabriele F, Conchedda M, Bortoletti G, Ecca AR}}</ref>（蠕虫具有几丁质的口器以固定肠壁）。最后，植物中的几丁质酶和水杨酸之间的联系已经建立，但是水杨酸与人类过敏之间存在假想的联系。<ref name="pmid1123257">{{cite journal|title=Food additives in clinical medicine|date=March 1975|journal=International Journal of Dermatology|issue=2|doi=10.1111/j.1365-4362.1975.tb01426.x|volume=14|pages=112–4|pmid=1123257|vauthors=Feingold BF}}</ref>

调节因物种而异，并且在生物体内，具有不同生理功能的几丁质酶将处于不同的调节机制下。例如，参与维护（比如重塑细胞壁）的几丁质是构成表达的。但具有专门功用的酶，如降解外源性几丁质或参与细胞分裂的，需要精确的基因时空调控。<ref name=":2">{{cite journal|title=Fungal chitinases: function, regulation, and potential roles in plant/pathogen interactions|date=May 2016|journal=Current Genetics|issue=2|doi=10.1007/s00294-015-0530-x|volume=62|pages=243–54|pmid=26527115|vauthors=Langner T, Göhre V}}</ref>

木霉的内切几丁质酶的调控依赖于N-乙酰葡萄糖酶，数据表明，在反馈循环中，几丁质的分解会产生[[N-乙酰葡萄糖胺]]，这有可能被采取并触发对chitinbiosidases的上调节。<ref>{{cite journal|title=The Nag1 N-acetylglucosaminidase of Trichoderma atroviride is essential for chitinase induction by chitin and of major relevance to biocontrol|date=July 2003|journal=Current Genetics|issue=4|doi=10.1007/s00294-003-0399-y|volume=43|pages=289–95|pmid=12748812|vauthors=Brunner K, Peterbauer CK, Mach RL, Lorito M, Zeilinger S, Kubicek CP}}</ref>

在[[釀酒酵母|酿酒酵母]]和ScCts1p（酿酒酵母几丁质酶1）的调节中，几丁质酶其中之一是通过降解隔膜中的几丁质参与[[细胞分裂]]后的细胞分离。<ref>{{cite journal|title=Chitinase is required for cell separation during growth of Saccharomyces cerevisiae|date=October 1991|journal=The Journal of Biological Chemistry|issue=29|volume=266|pages=19758–67|pmid=1918080|vauthors=Kuranda MJ, Robbins PW}}</ref>由于这些几丁质酶在细胞分裂中很重要，因此必须进行严格的调节和激活。具体而言，在[[有丝分裂]]后期必须在子细胞中激活Cts1的表达，并且该蛋白必须位于隔膜的子位置。<ref>{{cite journal|title=Yeast Cbk1 and Mob2 activate daughter-specific genetic programs to induce asymmetric cell fates|date=December 2001|journal=Cell|issue=6|doi=10.1016/S0092-8674(01)00596-7|volume=107|pages=739–50|pmid=11747810|vauthors=Colman-Lerner A, Chin TE, Brent R}}</ref>为此，必须与其他控制细胞不同阶段的调节网络进行协调，如Cdc14早期相位释放（FEAR）、有丝分裂退出（MEN）和Ace2p（转录因子）和细胞形态生成（RAM）的调节。<ref>{{cite journal|title=RAM: a conserved signaling network that regulates Ace2p transcriptional activity and polarized morphogenesis|date=September 2003|journal=Molecular Biology of the Cell|issue=9|doi=10.1091/mbc.E03-01-0018|volume=14|pages=3782–803|pmc=196567|pmid=12972564|vauthors=Nelson B, Kurischko C, Horecka J, Mody M, Nair P, Pratt L, Zougman A, McBroom LD, Hughes TR, Boone C, Luca FC}}</ref>总的来说，不同调节网络的整合使几丁质酶降解细胞壁的功能取决于[[細胞周期|细胞周期]]的阶段以及子细胞之间的特定位置。<ref name=":2" />

几丁质酶分子的某些部分，在植物防御中的功能相似，在结构上与[[橡膠|橡胶]][[乳胶]]中的促肝素或其他蛋白质几乎相同，可能会引发一种称为乳胶-水果综合征（latex-fruit syndrome）的过敏交叉反应。<ref>{{cite web|title=Latex-Fruit Syndrome and Class 2 Food Allergy|url=http://dmd.nihs.go.jp/latex/cross-e.html|work=Division of Medical Devices, Japan|accessdate=2020-10-05|||}}</ref>

几丁质酶具有广泛的应用，其中一些已经被工业实现。这包括将几丁质生物转化为有用的产品（例如[[肥料]]），生产不过敏，无毒，可生物相容和可[[生物降解]]的材料（已经生产出具有这些质量的[[隱形眼鏡|隐形眼镜]]，[[人造皮膚|人造皮肤]]和缝合线）以及增强的[[杀虫剂]]和[[杀菌剂]]。<ref name="update">{{cite journal|title=Chitinases: An update|date=January 2013|journal=Journal of Pharmacy & Bioallied Sciences|issue=1|doi=10.4103/0975-7406.106559|volume=5|pages=21–9|pmc=3612335|pmid=23559820|vauthors=Hamid R, Khan MA, Ahmad M, Ahmad MM, Abdin MZ, Musarrat J, Javed S}}</ref>