角蛋白酶及其研究进展

角蛋白在一般情况下很难被降解,工业上用高温、高压的办法降解角蛋白。然而,角蛋白酶能在温和的条件下降解角蛋白。本文对角蛋白的理化性质、发酵条件和分子生物学进行了综述。     

微生物角蛋白酶的分子生物学研究进展

角蛋白酶具有分解角蛋白的活性,在饲料,食品加工,环境废物处理等方面,具有广泛的应用前景。本文综述了微生物角蛋白酶的来源,角蛋白酶的理化性质,作用机理,基因分离和表达等分子生物学和基因工程研究进展,并对其应用前景进行了展望,对其今后的发展趋势进行了讨论。     

角蛋白酶的研究与应用前景

角蛋白酶(keratinase) 是一种可以特异性降解角蛋白的酶类,其来源广泛,多种微生物在羽毛降解过程中均可产生角蛋白酶。不同菌种来源的角蛋白酶,其结构、理化性质、活性和底物也不同。其在饲料行业、制革工业和环境废弃物处理等多个方面具有广泛的应用前景,能够产生巨大的社会效益和经济效益。本文系统总结了角蛋白酶的来源、分类、理化性质、作用机理及其在基因工程研究等方面的一些最新进展,简要介绍了其应用研究现状,并展望了角蛋白酶的应用前景。     

角蛋白酶研究进展

角蛋白酶（keratinase）是分解角蛋白的一类蛋白酶,应用广泛,如分解含角蛋白的毛发、羽毛、角蹄、鳞等等,而角蛋白的化学结构稳定,不溶于水,一般的蛋白酶对它们降解不起什么作用。只有角蛋白酶对角蛋白有分解活性,所以称这种酶为角蛋白酶。     

微生物角蛋白酶的特性及其应用研究进展

角蛋白作为家禽加工和农业废弃物的主要成分,因其结构中富含能抵抗普通蛋白酶和化学催化剂降解的稳定交联二硫键而难以被利用,因此每年都在环境中大量积累,造成了严重的环境污染。微生物角蛋白酶可将角蛋白废弃物转化为可再次利用的产物,带来了经济的可行性及环境的可持续发展。本文主要综述了角蛋白酶的生物化学特性、角蛋白酶的基本结构及其表达特性,总结了其应用价值及角蛋白降解机制,最后展望了微生物角蛋白酶的进一步研究方向。     

角蛋白酶的结构、功能及应用

角蛋白是广泛存在于羽毛及毛发中的难溶性蛋白质。角蛋白酶可以催化角蛋白的降解，在畜牧、皮革加工、医疗等领域中具有较大的应用价值与潜力。近年来，研究人员对角蛋白酶的来源、分类、结构、功能优化等方面进行了大量的研究，并取得了很多成果，为角蛋白酶的商业化应用提供了很好的基础。本文综述了角蛋白酶结构、功能、应用等方面的研究进展，并提出了今后的研究方向。     

角蛋白酶在真菌侵染皮肤过程中的作用

具有高度交联三维结构的角蛋白对各种物理、化学和一般性的蛋白水解酶攻击具有很强的抗性,但在底物的诱导下,皮肤真菌分泌的用蛋白酶可特异性地水解该蛋白。在真菌感染皮肤过程中,用蛋白酶与菌丝的机械侵入和化学还原作用配合,使病原菌获得营养和侵入皮肤。在抗真菌药物的配方中,加入角蛋白酶,可帮助活性因子通过皮肤屏障或抑制病原菌繁殖。     

角蛋白单体获得及诱导S.maltophilia DHHJ产角蛋白酶研究

可降解羽毛微生物能以羽毛粉为唯一营养源生长,而羽毛粉是一种大颗粒的不溶性底物,不能直接进入细胞内作为营养源同时作为一级信使来诱导酶基因表达.本文通过化学还原法水解羽毛得到可溶性羽毛角蛋白溶液,利用电泳和质谱验证其分子量约10 kD,为角蛋白单体.分别以该可溶性羽毛角蛋白及角蛋白单体酶解片段为诱导源,在无诱导源、羽毛粉为对照的情况下,测定72 h内嗜麦芽窄食单胞菌(S.maltophilia)DHHJ产生的角蛋白酶的酶活.在无诱导源时,角蛋白酶基因表现本底表达(0.5 U/mL);培养基中添加羽毛粉及角蛋白单体时,角蛋白酶表达量高,分别可达15 U/mL和20 U/mL.并且角蛋白单体酶解片段诱导酶表达较低(2.3 U/mL).该结果初步表明,水溶性角蛋白单体作为信号源与细菌细胞接触或进入细胞内,控制角蛋白酶基因表达.该结果为细菌降解角蛋白分子机制研究奠定基础.     

Bacillus coagulans X3角蛋白酶的酶学性质及其应用研究

为了提高凝结芽孢杆菌(Bacillus coagulans)X3角蛋白酶的水解效率,对其粗酶液的酶学性质及降解羽毛角蛋白的效果进行了研究。结果表明,粗酶液的最适反应温度为60℃,最适pH为7.0～8.0,在70～80℃时具有较好的热稳定性。金属离子中Ca²⁺、Mn²⁺对角蛋白酶活性起促进作用,Cu²⁺、Ni²⁺强烈抑制角蛋白酶活性,而Na⁺、Mg²⁺、Fe³⁺对酶活性无显著影响。化学试剂苯甲基磺酰氟(PMSF)、乙二胺四乙酸(EDTA)对酶活性有较强的抑制作用,β-巯基乙醇和二硫基苏糖醇(DTT)可显著提高酶活性,十二烷基磺酸钠(SDS)和二甲基亚砜(DMSO)对酶活性没有显著影响。优化条件下降解羽毛,产物中游离氨基酸的总量高达4.322 6 mg/mL,主要种类为缬氨酸、苯丙氨酸、酪氨酸、谷氨酸。研究结果为菌株X3酶解角蛋白废弃物提供了技术支撑。     

皮肤癣菌外分泌角蛋白酶的研究进展

近年来角蛋白酶成为皮肤癣菌致病机制的研究热点,角蛋白酶在真菌的自身营养、组织入侵及控制宿主的防御机制上都发挥着重要的作用,同时也是研究真菌疫苗的一个候选抗原。     

Purification and Characterisation of Keratinase from a Thermotolerant Feather-degrading Bacterium

Summary Isolation and identification of a thermotolerant feather-degrading bacterial strain from Thai soil as well as purification and properties of its keratinase were investigated. The thermotolerant bacterium was identified as Bacillus licheniformis. The keratinase was purified to homogeneity by three-step chromatography. The purified enzyme exhibited a high specific activity (218 U mg⁻¹) with 86-fold purification and 25% yield. The enzyme was monomeric and had a molecular mass of 35 kDa. The optimum pH and temperature for the enzyme were 8.5 and 60 °C, respectively. The enzyme activity was significantly inhibited by PMSF and partly inhibited by EDTA and iodoacetamide, but was stimulated by metal ions. It hydrolysed soluble proteins with a relative activity of 4–100% and insoluble proteins, including keratins, with a relative activity of 3–35%. Therefore, the enzyme could improve the nutritional value of meat- and poultry-processing wastes containing keratins, collagen and gelatin.     

角蛋白降解菌的筛选及其UV诱变选育

从长年堆积废羽毛的土壤,屠鸡场下水道、池塘底污泥中分离出一株角蛋白降解菌C-1,摇瓶发酵测得其角蛋白酶活达35.6U,经形态观察和生理生化鉴定该菌株属于芽孢杆菌属.对菌株进行Uv诱变,在照射时间为100 s下得到一株产角蛋白酶活较高突变株C-1-4,其酶活比原始出发菌株提高了122%,且遗传性状稳定.     

Keratinase Production by Newly Isolated Antarctic Actinomycete Strains

Summary The ability of actinomycete strains newly isolated from Antarctic soils to produce keratinolytic enzymes during growth on sheep wool waste was investigated. The strains which displayed highest keratinase activity and identified as Streptomyces flavis 2BG (mesophilic) and Microbispora aerata IMBAS-11A (thermophilic) were selected for a more detailed analysis. The addition of starch to the growth medium affected keratinase secretion by both strains. After 5 days of cultivation, a 6-fold increase in keratinase activity of strain 11A was observed in the presence of 11 g starch/l and a 9-fold increase in keratinase activity of the strain 2BG in the presence of 5 g starch/l. The results obtained showed that both newly isolated strains are very promising for effective processing of native keratinous wastes. To our knowledge, this is the first report of Antarctic actinomycete strains that were able to grow on keratin-containing wastes by producing keratinolytic enzymes.     

Keratin degradation by fungi isolated from the grounds of a gelatin factory in Jabalpur,India

The ability of five keratinophilic fungi, i.e., Chrysosporium indicum, Geotrichum candidum, Gymnoascoideus petalosporus, Scopulariopsis brevicaulis, and Talaromyces trachyspermus, to digest human hair keratin in stationary culture has been studied. Degradation of human scalp hair was studied by determination of cysteine, cystine, inorganic sulfate, thiosulfate, total protein, keratinase and change in alkalinity of culture filtrate. Gymnoascoideus petalosporus showed maximum degradation as compared to remaining isolates when grown on human scalp hair as the sole source of nutrients in vitro.     

降解鸡毛真菌板蜡蚧的鉴定及产酶培养优化

鉴定降解鸡毛真菌并通过单因素和正交实验优化其产角蛋白酶发酵培养条件.从加入鸡毛粉钓饵的医院花坛土中分离筛选获得3株角蛋白高效降解真菌,利用形态学和分子系统学鉴定均为板蜡蚧(Lecani-cillium testudineum).单因素实验表明,对优选菌株1Y2-12产酶能力具促进作用的碳源为乳糖,氮源为酵母膏,无机离子...     

提高微生物角蛋白酶产量和催化性能的研究进展

角蛋白酶是一类能水解难溶性角蛋白废物的广谱蛋白酶,在饲料、肥料、医疗、制革和洗涤剂等领域具有良好应用前景。但目前已报道的天然角蛋白酶存在产量低、活性低和稳定性差的问题,限制了角蛋白酶的应用。提高角蛋白酶产量和催化性能的策略主要包括寻找新的角蛋白酶资源、改造天然宿主、异源表达、优化发酵条件和通过随机突变与（半）理性设计修饰角蛋白酶。利用上述一种或多种策略,有望提高角蛋白酶产量和催化性能,缩短生产时间,降低生产成本,促进角蛋白酶在各领域的应用。     

Crystal structure of fervidolysin from Fervidobacterium pennivorans, a keratinolytic enzyme related to subtilisin

Structure-forming fibrous proteins like keratins, gelatins and collagens are degraded only by a few proteases as their tight packing limits access to the potential cleavage sites. To understand the keratin degradation in detail, we describe the first crystal structure of a keratin-degrading enzyme (keratinase), fervidolysin, from Fervidobacterium pennivorans as an immature form with propeptide (PD)-bound. The 1.7A resolution crystal structure shows that the protease is composed of four domains: a catalytic domain (CD), two beta-sandwich domains (SDs), and the PD domain. A structural alignment shows a distant relationship between the PD-CD substructure of fervidolysin and pro-subtilisin E. Tight binding of PD to the remaining part of the protease is mediated by hydrogen bonds along the domain surfaces and around the active cleft, and by the clamps to SD1 and SD2. The crystal structure of this multi-domain protein fervidolysin provides insights into proenzyme activation and the role of non-catalytic domains, suggesting a functional relationship to the fibronectin (FN)-like domains of the human promatrix metalloprotease-2 (proMMP-2) that degrades the fibrous polymeric substrate gelatin.