木聚糖降解酶系统

介绍了木聚糖降解酶系统的的多种组成成分,各个酶的生物化学特性,并着重介绍了木聚糖降解酶系统中的主要酶──木聚糖酶的结构、基因特征及其代谢调控机理。     

高效木聚糖降解酶系定制的新进展与挑战

木聚糖是植物细胞壁中含量最丰富的非纤维素多糖,大约占陆地生物质资源的20%-35%。不同物种来源的木聚糖结构因取代方式不同而具有广泛的异质性,这对生物质资源向生物燃料和其他高值产品高效转化提出了重大挑战。因此,需要开发由不同类型酶组成的最佳混合物以有效糖化木聚糖类底物。但是针对特定类型的底物设计高效降解酶系十分困难,应考虑底物的类型、底物的组成和物理性质、多糖的聚合度以及不同降解酶组分的生化性质等。本文从不同植物木聚糖的结构异质性与合成复杂性方面展示了其抗降解屏障,同时介绍了木聚糖主链降解酶系及侧链降解酶系的多样性以及协同降解作用,综述了复杂生境中微生物种群产生的混合酶系、降解菌株产生的高效酶系,以及基于特定木聚糖底物改造并定制简化高效的酶系统。随着不同种类木聚糖精细结构和木聚糖降解酶底物特异性的深入研究,针对特定底物类型进行绿色高效木聚糖酶系定制,加速木聚糖类底物的降解,从而实现木质纤维素资源的绿色高值化利用。     

乙酰木聚糖酯酶研究进展

半纤维素是一类丰富可再生而又亟待开发利用的生物质资源,将半纤维素降解为糖类进而生产木糖醇及其它化学品是利用生物质资源的关键一步。乙酰木聚糖酯酶是降解半纤维素的一个重要酶,它能够水解乙酰化木聚糖中的木糖残基上的2位和3位的O 乙酰基,在工业、农业及食品业具有广阔的应用前景。综述了乙酰木聚糖酯酶的分类、酶学性质、催化机制、基因克隆和协同酶解等方面的研究进展,同时对该研究进行了展望。     

微生物木聚糖酶的研究进展及其在食品领域的应用

木聚糖是半纤维素的主要组成成分,也是自然界第二丰富的可再生资源。木聚糖的结构稳定、组成复杂,很难在自然条件下自我降解,只有通过多种酶组成的木聚糖酶系的协同作用才可以更好地水解木聚糖或含有木聚糖的底物。木聚糖酶系主要由微生物产生,不同来源的木聚糖酶的性质存在较大差异。介绍了木聚糖水解酶系的组成和作用机理,木聚糖酶的分类和酶学性质,并对木聚糖酶在食品领域的应用进行了综述。     

阿魏酸酯酶基因工程菌研究进展

阿魏酸酯酶能水解阿魏酸、多聚阿魏酸与木聚糖以及木质素之间形成的酯键,有利于植物细胞壁的降解。介绍阿魏酸酯酶的微生物来源、阿魏酸酯酶基因工程菌构建和阿魏酸酯酶与其他酶相互协同作用等的研究进展。     

食用菌半纤维素酶系研究进展

半纤维素是一类取之不尽而又亟待开发利用的碳水化合物。对食用菌半纤维素酶系的研究已经积累了诸多资料,主要包括β-1,4-内切木聚糖酶、β-木糖苷酶、α-阿拉伯呋喃糖苷酶、乙酰木聚糖酯酶、α-葡萄糖醛酸酶的研究。主要对半纤维素酶系,尤其是木聚糖酶的生物化学与分子生物学研究进行了简要概括,包括结构、酶学性质、基因的克隆与表达等,并综述了在食用菌生产中半纤维素酶活性的变化,最后展望了食用菌半纤维素酶系今后的主要研究方向。     

阿魏酸酯酶基因克隆表达调控及其应用进展

阿魏酸酯酶作为微生物降解植物多糖的酶系的一部分,其从细胞壁中降解多糖获得芳香酸和单多糖的能力越来越受到重视.主要介绍了阿魏酸酯酶研究进展,包括阿魏酸酯酶的研究现状,酶-底物分子对接模型、阿魏酸酯酶基因克隆表达、重组与调控以及应用.     

微生物木聚糖降解酶研究进展及应用前景

木聚糖是植物半纤维素的主要成分,它是除纤维素外,自然界中最为丰富的多糖。木聚糖的基本结构单元是由β－１．４或β－１．３糖苷键连接的多聚木糖链,在Ｄ－木糖的第二位氧上连接有Ｄ－葡萄糖醛酸或４－Ｏ－甲基葡萄糖醛酸或在第三位氧上连接有Ｌ－阿拉伯呋喃糖。有些木聚糖还在第二或第三位氧上发生乙酰化。不同来源的木聚糖在结构上有一定差异。木聚糖酶是一类木聚糖降解酶系（表１）,对降解自然界大量存在的半纤维素起着重要作用。它们不但可以降解木聚糖生成木糖,而且能以农作物残渣中的半纤维素为原料生产经济价值较高的产品。由…     

β-木糖苷酶及其在纤维素乙醇生产中的应用研究进展

将木质纤维素类生物质生物转化生产液体燃料,如纤维素乙醇和大宗化学品,对缓解当前人类社会面临的能源和资源危机以及保护环境具有重要意义。半纤维素是木质纤维素类生物质的主要组成成分之一,它的生物降解转化对实现木质纤维素生物炼制意义重大。由于半纤维素糖种类的多样性和半纤维素结构的复杂性,需要一个复杂的半纤维素酶系才能完成对半纤维素的有效降解。除了木聚糖酶等以外,β-木糖苷酶也是半纤维素酶系的主要组分。在半纤维素降解过程中,β-木糖苷酶将木聚糖酶的水解产物木寡糖和木二糖水解为木糖,不仅在木聚糖的彻底降解过程中起着重要作用,而且可以缓解木寡糖对木聚糖酶和纤维素酶的抑制作用。该文综述了目前在β-木糖苷酶方面的研究进展,包括β-木糖苷酶的分类、酶学性质、酶结构及其催化机制、基因的克隆与表达等,并对β-木糖苷酶在纤维素乙醇生产中的应用情况进行了简述。     

微生物木聚糖降解酶系统

木聚糖类半纤维素是产量仅次于纤维素的植物多糖 ,其结构要比纤维素复杂得多 ,完全降解木聚糖 ,实现植物残体的生物转化需要多种水解酶 (即木聚糖降解酶系统 )的协同作用。木聚糖酶在食品、饲料、纺织、能源工业 ,特别是在纸浆和造纸工业中有着广阔的应用前景 ,如人们将极端嗜热和嗜碱菌的木聚糖酶基因克隆到现有工程菌中生产工业用酶 ,用于纸浆的生物漂白和饲料加工。但是木聚糖资源的开发利用要求完整的酶系统。人们通过对具有木聚糖降解酶系统微生物的研究 ,运用基因工程技术将其构建成发酵工程菌 ,直接利用半纤维素生产单细胞蛋白 ;或者…     

Production of cellulolytic enzymes containing cinnamic acid esterase from Schizophyllum commune

To develop enzyme preparations capable of digesting plant biomass, we examined the production of cinnamic acid esterase as well as cellulolytic and xylanolytic enzymes in cultures of Schizophyllum commune. The cinnamic acid esterase was produced in the cultures containing solid cellulosic substrates, with production being enhanced by delignifying the wood powder. This indicates that these esterases are produced by cellulose, despite their substrates being phenolic compounds. Cellulolytic and xylanolytic enzymes, with the exception of α-arabinofuranosidase, were also produced in cultures containing cellulosic substances. These results show that enzyme preparation can have high activity of cinnamic acid esterase and cellulolytic and xylanolytic enzymes when S. commune is incubated in the presence of cellulose. These enzyme preparations will be useful for digesting plant biomass and for releasing cinnamic acid derivatives from plant cell walls.     

Microbial carboxylic ester hydrolases (EC 3.1.1) in food biotechnology

Ester linkages between carboxylic acid groups and hydroxyl groups are basic to the structure of carboxyesters and lipids, and occur commonly as modifications of polysaccharide molecules. Microorganisms produce enzymes which hydrolyse the carboxylic ester linkages in substrates which are being utilized for growth. Such esterase reactions are frequently easily reversible, depending on the concentration of reactants or availability of water. The importance of esters as flavour compounds has resulted in the selection of yeast strains which produce esters in beverage fermentation. The synthetic potential of triacylglycerol lipases (EC 3.1.1.3) has been exploited by use of the purified enzymes in environments of low water activity. The techniques of molecular biology facilitate analysis of the homology between carboxylesterase enzymes and a detailed knowledge of structure and specificity provides the opportunity to modify enzymes to suit particular applications in biotechnology.
Esterase activity can be assayed conveniently by using synthetic chromogenic esters of naphthol or nitrophenol. Naphthyl and nitrophenyl acetates are readily hydrolysed by a wide range of enzymes including lipases (Hofelmann et al. 1985; Brahimi-Horn et al. 1990; Gilbert et al. 1991), serine protease (Klapper et al. 1973) and acetylxylan esterase (Lee et al. 1987). Electrophoretic separation followed by detection using chromogenic esters has demonstrated polymorphism of esterase enzymes and has been used to type strains of bacteria (Goullet & Picard 1990, 1991; Picard & Goullet 1990) but was less discriminating with yeasts (Campbell et al. 1972) and edible mushrooms (Itavaara 1988).     

Production of acetyl esterase during wood biodegradation byCoriolus versicolor

A role of acetyl esterase in wood biodegradation byCoriolus versicolor was examined by the assay of enzyme production and the chemical analysis of decayed wood meal of Japanese beech (Fagus crenata). Enzyme assay demonstrated that the degradation proceeded in two stages and acetyl esterase production was correlated with the cellulolytic and xylanolytic enzyme production in the second stage, not with the production of phenol-oxidizing enzymes. From the results of chemical analysis, acetyl and xylose contents in wood meal were observed to decrease simultaneously in the second stage. In contrast, rapid decrease of lignin was recognized during the initial three wk of incubation, and it was closely related with the production of phenol-oxidizing enzymes in the first stage. These results show that acetyl esterase ofC. versicolor participates in the degradation of acetylxylan and acts with the cellulolytic and xylanolytic systems, not with the ligninolytic system.     

Synergy between xylanases from glycoside hydrolase family 10 and family 11 and a feruloyl esterase in the release of phenolic acids from cereal arabinoxylan

The bioconversion of waste residues (by-products) from cereal processing industries requires the cooperation of enzymes able to degrade xylanolytic and cellulosic material. The type A feruloyl esterase from Aspergillus niger, AnFaeA, works synergistically with (1→4)-β-d-xylopyranosidases (xylanases) to release monomeric and dimeric ferulic acid (FA) from cereal cell wall-derived material. The esterase was more effective with a family 11 xylanase from Trichoderma viride in releasing FA and with a family 10 xylanase from Thermoascus aurantiacus in releasing the 5,5′ form of diferulic acid from arabinoxylan (AX) derived from brewers’ spent grain. The converse was found for the release of the phenolic acids from wheat bran-derived AXs. This may be indicative of compositional differences in AXs in cereals.     

Immunohistochemical localization of rat submandibular gland esterase B (homologous to the RSKG-7 kallikrein gene) in relation to other serine proteases of the kallikrein family.

The rat submandibular gland contains several members of the kallikrein family. In the present study we purified and raised an antiserum against one of these enzymes, i.e., esterase B, which was first described by Khullar et al. in 1986. N-terminal amino acid analysis revealed complete homology between esterase B and the kallikrein family gene RSKG-7. For characterization of the antiserum, flat-bed isoelectrofocusing with immunoblotting was superior to immunoelectrophoresis and double immunodiffusion in detecting and identifying crossreacting proteins. This was due to the fact that kallikrein-like enzymes were readily separated by isoelectrofocusing, and immunoreactivity was easily detected by the sensitive peroxidase-anti-peroxidase staining after blotting onto nitrocellulose membrane. Immunohistochemical controls were carried out accordingly, including homologous as well as crossreacting antigens. In the submandibular gland, esterase B was detected exclusively in all granular convoluted tubular cells, co-localized with tissue kallikrein and tonin. Some staining was also observed in striated duct cells; however, this staining reaction was induced by cross-reactivity with kallikrein, since staining was abolished by addition of kallikrein as well as esterase B to the primary antiserum. It was therefore concluded that like tonin and antigen gamma, but unlike kallikrein, esterase B was not detected in the striated ducts of the submandibular, parotid, or sublingual glands. This separation in anatomic distribution between esterase B and kallikrein may indicate that prokallikrein activation is not the only biological function of esterase B.     

Genetic variation as a tool for histochemical localization of a nonspecific esterase

Summary A prominent esterase activity was demonstrated histochemically in the straight portion of the proximal tubules in kidney of the mouse strain DBA/2J after inhibition with bis-p-nitrophenyl phosphate and subsequent staining, using 5-bromoindoxyl acetate as substrate. In the strain PUC/1Fre, the corresponding esterase was only weakly expressed. By comparing data from the literature (von Deimling et al. 1981) with the characteristic features of this kidney esterase including substrate preference, sensitivity to inhibitors, solubility, histochemical location, and strain differences, it was concluded that it was identical with the previously electrophoretically defined esterase-16.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday     

Genetic variation as a tool for histochemical localization of a nonspecific esterase

A prominent esterase activity was demonstrated histochemically in the straight portion of the proximal tubules in kidney of the mouse strain DBA/2J after inhibition with bis-p-nitrophenyl phosphate and subsequent staining, using 5-bromoindoxyl acetate as substrate. In the strain PUC/1Fre, the corresponding esterase was only weakly expressed. By comparing data from the literature (von Deimling et al. 1981) with the characteristic features of this kidney esterase including substrate preference, sensitivity to inhibitors, solubility, histochemical location, and strain differences, it was concluded that it was identical with the previously electrophoretically defined esterase-16.     

Influence of vanillin on the production of cellulolytic and xylanolytic enzymes from a wood-rotting fungus,Coriolus versicolor

To examine the influence of a phenolic compound on the production of cellulolytic and xylanolytic enzymes of a woodrotting fungusCoriolus versicolor, a two-dimensional map of enzyme activity was constructed with various concentrations of cellobiose and vanillin. The productions of CMCase, xylanase, β-glucosidase, and β-xylosidase increased with higher cellobiose concentration and were markedly enhanced by addition of vanillin. Higher ratio of vanillin/cellobiose activated the production of these enzymes. Only acetyl esterase, which is not actively produced at the ligninolytic stage ofC. versicolor, was inhibited by the monolignol vanillin. As the presence of vanillin is considered to approximate conditions of wood decay more closely than its absence, the present result demonstrates that addition of vanillin, a phenolic compound, enhanced the production of cellulolytic and xylanolytic enzymes for wood cell wall degradation.