固定化邻单胞杆菌降解高浓度直链烷基苯磺酸钠的研究

邻单胞杆菌(Plesiomonas sp.90-1)经海藻酸钠固定后,忍耐和降解100 ppm的高浓度LAS的能力较同样浓度的游离细胞分别提高4.875倍和0.77倍。我们研究了最佳固定条件和固定化细胞的最佳降解条件。该固定化细胞米氏常数Km和最大反应速度V_m分别为1061μmol和43.5μmol/h。此外,利用多因子正交法确定了降解酶活恢复的最佳培养条件,在此条件下培养的固定化细胞的降解酶活可提高116％。     

固定化条件对葡萄糖酶电极响应性能的影响

用微铂盘电极和交联法制得的酶膜构成葡萄糖酶电极，测定其电流响应特性，研究了酶的固定化条件：酶含量以及载体蛋白和交联剂的用量等，对响应特性的影响。提出较适宜的酶电极制备方法，并检测了所得的电极在不同ｐＨ溶液中的灵敏度，指出其最佳操作条件。     

新疆蜗牛酶的研制

以野生蜗牛嗉囊为原料提取蜗牛酶产品,检测所含纤维素酶、淀粉酶的活性,对其蜗牛酶产品进一步测试,结果表明新疆蜗牛酶中的纤维素酶活力为450U/g淀粉酶为405U/g。验证了新疆蜗牛酶中纤维素酶的活力很高。     

火焰原子光谱法快速测定指甲中的钙镁钾

建立了非完全消化-火焰原子光谱法快速测定指甲中钙、镁、钾的分析方法。在低温下用浓硝酸消解样品,可获得均匀、透明的样品溶液。用发射法测定钙、钾,以吸收法测定镁。以Sr2+作为钙的释放剂及钾的消电离剂。对样品处理条件、化学干扰、试液与空白溶液粘度一致性、背景吸收干扰及检出限进行了考察。测定结果的相对标准偏差小于2.2%,测定结果与灰化法一致,相对误差小于±1.2%。方法简便、准确。     

Study on screening and cultivation conditions of xylanase-producing alkalophilic bacterial

Xylanisthemajorcomponentofplantcellwallsandthemostabundantpentosaninnature.Xylancontainsβ 1,4 linkedd xylosebackboneswitharabinose,4 O methyl d glucuronicacid,andaceticacidsubstituents[1 ] .Thexylan degradingen zymesincludeendoxylanase(1,4 β d xylanxylanohydrolase;EC3.2 .1.8)and β xylosidase (1,4 β d xylanxylanohydrolase;EC 3.2 .1.37) .xylanasedegradesthexylanbackboneintoxylo bioseandxylooligosaccharides,whileβ xylosidasereleasesxylosylresiduesfromthenonreducingendsofxylooligosaccha…     

Role of Cys221 and Asn116 in the zinc-binding sites of the Aeromonas hydrophila metallo-β-lactamase

The CphA metallo--lactamase produced by Aeromonas hydrophila exhibits two zinc-binding sites. Maximum activity is obtained upon binding of one zinc ion, whereas binding of the second zinc ion results in a drastic decrease in the hydrolytic activity. In this study, we analyzed the role of Asn116 and Cys221, two residues of the active site. These residues were replaced by site-directed mutagenesis and the different mutants were characterized. The C221S and C221A mutants were seriously impaired in their ability to bind the first, catalytic zinc ion and were nearly completely inactive, indicating a major role for Cys221 in the binding of the catalytic metal ion. By contrast, the binding of the second zinc ion was only slightly affected, at least for the C221S mutant. Mutation of Asn116 did not lead to a drastic decrease in the hydrolytic activity, indicating that this residue does not play a key role in the catalytic mechanism. However, the substitution of Asn116 by a Cys or His residue resulted in an approximately fivefold increase in the affinity for the second, inhibitory zinc ion. Together, these data suggested that the first zinc ion is located in the binding site involving the Cys221 and that the second zinc ion binds in the binding site involving Asn116 and, presumably, His118 and His196.Received 3 March 2003; received after revision 4 August 2003; accepted 25 August 2003     

Changes in calpastatin localization and expression during calpain activation: a new mechanism for the regulation of intracellular Ca<Superscript>2+</Superscript>-dependent proteolysis

The amount of calpastatin directly available in cytosol is under the control of [Ca²⁺] and [cyclic AMP]. Prolonged calpain activation also promotes degradation of calpastatin. The fluctuation of calpastatin concentration in cell soluble fraction is accompanied by an initial decrease in calpastatin gene expression, followed by a fivefold increase in its expression when the inhibitor protein is degraded. This process can be conceptualized as a mechanism to regulate calpastatin availability in the cell. This conclusion is supported by the fact that calpain, the other component of this proteolytic system, undergoes changes in its levels of expression in a much more limited manner. Furthermore, this process can be observed both in cells exposed to different natural stimuli, or in other cell lines. Modification of calpastatin gene expression might represent a new tool for the in vivo control of the regulatory machinery required for the modulation of Ca²⁺-dependent proteolysis.Received 18 July 2003; received after revision 3 September 2003; accepted 23 September 2003     

紫外线诱变康宁木霉提高酶活力的研究

通过对康宁木霉菌种的诱变、筛选和固体发酵培养,研究了培养基、培养时间、诱变时间及pH值对诱变菌所产酶的活力的影响．结果表明,康宁木霉经诱变5min,在pH为6．0的玉米秸PDA培养基上培养72h,产生的C1酶和Cx酶的酶活力较高,C1酶的酶活力由73u／g提高到176u／g,增加了2．41倍,Cx酶的酶活力由798u／g提高到2069u／g,增加了2．59倍．     

Fluorescence spectra and enzymatic property of hemoglobin as mimetic peroxidase

0　IntroductionHemoglobin(Hb)isthemajorhemeproteinofredbloodcells(RBCs)andisresponsibleforthetransportofoxygentothetissues.ThefunctionofHbdependsupontheabilityoffer rousironinthehemegrouptobindandreleaseoxygen .Despiteitsprincipalroleasanoxygen carrier,theHbmoleculepossessesdifferentenzymaticactivities[1 ] andamethodwasdevelopedforthedeterminationofHbbasedonitsenzymaticactivityfortheox idationofo phenylenediamine (OPDA)withH2 O2 asanoxi dant[2 ] .Hbasamimeticenzymeofperoxidase ,cancataly…     

不同温度对双齿多刺蚁养殖及其保护酶系的影响

在不同温度下长期养殖双齿多刺蚁,观察其存活率和活动状况,测定了不同温度对其SOD,POD,CAT活力的影响,并进行了保护酶活性和存活率的相关分析.实验表明,在较低和较高温度下其存活率明显低于10-40℃测定值.在40-45℃时,酶的活性随着温度升高急速下降;在-5-10℃时,酶的活性随着温度降低而下降.保护酶活性和存活率密切相关.10℃以下的低温和40℃以上的高温对其有不同程度的伤害,其适宜温区为10-40℃,最适温度为20-30℃.