植酸酶的研究进展

植酸酶是催化植酸及植酸盐水解成肌醇和无机磷酸的一类酶的总称。植酸酶作为一种新型酶制剂,添加于食品和饲料中,能消除植酸引起的抗营养作用,提高蛋白质的生物利用率。本文综述有关植酸酶的分子结构、作用机理、生物学特征、基因结构的研究。     

脂环酸芽孢杆菌D-1的耐盐内切葡聚糖酶基因克隆、表达与酶学性质北大核心CSCD

【目的】克隆温泉中嗜热嗜酸的脂环酸芽孢杆菌D-1(Alicyclobacillus tengchongensis CGMCC1504)的内切葡聚糖酶基因gluE1,并对该酶进行序列分析和重组酶的酶学特性分析。【方法】通过全基因组测序获得gluE1全长,并对其氨基酸序列(GluE1)进行分析。将gluE1重组到载体p EASY-E2中并转化到大肠杆菌BL21(DE3)中异源表达,利用组氨酸标签纯化GluE1并进行酶学性质分析。【结果】gluE1与NCBI数据库中GH5的内切葡聚糖酶具有较高的相似性,全长1020 bp,GC含量50.5%,编码339个氨基酸(40.45 k Da)。GluE1与数据库中序列的最高一致性为97%,与其余纤维素酶的一致性<60%。GluE1可水解CMC-Na、可溶性淀粉和大麦β-葡聚糖,表观最适pH为6.5,pH 5.0–10.0稳定并维持60%以上的酶活性。GluE1的表观最适温度为55℃,在37℃下稳定。在55℃ pH 6.5条件下,GluE1对大麦β-葡聚糖的K_m、V_(max)和k_(cat)分别为8.58 mg/mL、416.67 U/mg和280.90 s^(–1)。GluE1受Ag^+、Hg^(2+)及SDS抑制,β-巯基乙醇、Pb^(2+)、Mg^(2+)、Ca^(2+)和Na^+对GluE1有微弱的促进作用,NaCl对GluE1的影响不大,加入30%的NaCl,仍有64%以上的酶活性;经30%的NaCl在37℃下处理60 min,仍能保持93%以上的活性。【结论】首次报道从Alicyclobacillus属的细菌中克隆得到内切葡聚糖酶基因并对其酶学性质进行研究,GluE1具有良好的pH稳定性和有较强的耐盐性,可能具有更大应用潜力。     

家蝇幼虫同工酶研究

本通过聚丙烯酰凝胶电泳法对家蝇幼虫体内的过氧化物酶、乳酸脱氢酶、苹果酸脱氢酶、酯酶和超氧化物歧化酶,以及对超氧化物歧化酶的特性进行了研究。实验结果为家蝇幼虫资源开发利用提供了理论依据。     

Magnetic characterizations of nickel hyperaccumulating plants (Planchonella oxyhedra and Rinorea bengalensis) from Halmahera,Indonesia

Magnetic minerals, such as magnetite and hematite, have been reported to be present, in particular, leaves as biogenic particles. The magnetic minerals and properties of Ni hyperaccumulators have not previously been reported in the literature. This study aimed to characterize the magnetic properties of two Ni hyperaccumulating plant species, R. bengalensis and P. oxyhedra, which grow in an ultramafic region on Halmahera Island, Indonesia. For comparison, similar characterization was carried out on two non-hyperaccumulating plant species which grow in the same region. Concentrations of Ni, Fe, and Mn in the leaves of the hyperaccumulating plants were measured using atomic absorption spectroscopy (AAS) and their magnetic properties were characterized using measurements of magnetic susceptibility, low temperature magnetic susceptibility, and hysteresis curves. The results show that, compared to the non-hyperaccumulating plants, the Ni hyperaccumulating plants have higher concentrations of Ni and similar concentration of Fe. The magnetic susceptibilities of hyperaccumulating plants are positive, and those of non-hyperaccumulating plants are negative. This suggests that the abundance of Ni, rather than Fe, may control the magnetic properties of Ni hyperaccumulating plants. This probable connection between Ni concentration and plant magnetic properties could be advantageous for identifying hyperaccumulators, and should, therefore, be explored further.     

Phosphorylation of aortic plasma membranes by protein kinase C

A calcium-sensitive, phospholipid-dependent protein kinase (protein kinase C) and its three isozymes were purified from rat heart cytosolic fractions utilizing a rapid purification method. The purified protein kinase C enzyme showed a single polypeptide band of 80 KDa on SDS-polyacrylamide gel electrophoresis, and was totally dependent on the presence of Ca²⁺ and phospholipid for activity. Diacylglycerol was also found to stimulate enzymatic activity. Autophosphorylation of the purified PKC showed an 80 KDa polypeptide. The identity of the purified protein was also verified with monoclonal antibodies specific for PKC. Further fractionation of the purified PKC on a hydroxylapatite column yielded three distinct peaks of enzyme activity, corresponding to type I, II and III based on similar chromatographic behaviour as the rat brain enzyme. All three forms were entirely Ca^2– and phosphatidylserine dependent. Type II was found to be the most abundant. Type I was found to be highly unstable. PKC activity studies demonstrate that types II and III isozymic forms are different with respect to their sensitivity to Ca²⁺.Abbreviations PKC Protein Kinase C - SDS Sodium Dodecyl Sulfate - PAGE Polyacrylamide Gel Electrophoresis - K_m Michaelis constant - NBT Nitro-Blue Tetrazolium - BCIP 5-Bromo-4-Chloro-3-Indolyl Phosphate     

Vector representations and related matrices of DNA primary sequence based on L-tuple

We consider to construct 4^L-components vectors for a DNA primary sequence based on the L-tuple. For two DNA sequences, using the corresponding vectors, we construct a set of L × L matrices called related matrix. The mathematical characterization from the constructed matrices have been selected to characterize the degree of similarity between the two DNA sequences. The search for similar sequences of a query sequence from a database of 39 library sequences and the construction of phylogenetic tree of H5N1 avian influenza virus illustrate the utility of the matrices for DNA sequences.     

来源于芽孢杆菌HJ14耐热酯酶的克隆表达、酶学性质及降解邻苯二甲酸二乙酯研究北大核心CSCD

【目的】克隆芽孢杆菌HJ14的酯酶基因Est Z1并利用大肠杆菌表达得到相应的酯酶,分析重组酯酶的酶学性质和对邻苯二甲酸二乙酯(Diethyl phthalate,DEP)的降解。【方法】特异性扩增酯酶基因Est Z1并对其全长测序,分析其氨基酸序列。利用p EASY-E2表达系统将Est Z1转化到Escherichia coli BL21(DE3)中完成异源表达。根据组氨酸标签纯化Est Z1,研究其酶学性质并利用HPLC和LC/MS检测系统定性分析其对DEP的降解。【结果】Est Z1全长903 bp,编码300个氨基酸残基,蛋白分子量33.84 k Da。Est Z1氨基酸序列分析结果显示,与NCBI数据库收录的HSL-like家族酯酶相似度最高可达到98%。酶学性质分析结果显示,Est Z1可水解碳链长度较短的p-NP底物,最适底物为p-NPC4(p-NP butyrate)。Est Z1的最适p H和最适温度分别为9.0和50°C,并且在p H 7.0–9.5和40–70°C范围内保持50%以上的酶活,为耐热碱性酯酶。Est Z1对多数金属离子和化学试剂保有良好的抗性。Est Z1可将DEP水解生成相应的单酯和醇。【结论】本文报道了Bacillus sp.HJ14来源的酯酶基因并对其在大肠杆菌中表达获得的重组酶的酶学性质进行研究,Est Z1具有良好的碱性p H耐受性和热稳定性,能够部分降解DEP,本研究对邻苯二甲酸酯类的生物降解有一定的参考意义。