Limited proteolysis of lactate dehydrogenase from procine heart with trypsin: Characterization and reactivation of the fragments

Summary The ternary complex formed by native lactate dehydrogenase (LDH) from porcine heart, NAD⁺ and sulfite, was digested with trypsin over a period of 12–16 h³. After removal of the ligands and residual native lactate dehydrogenase by ion exchange chromatography dimers were obtained which were almost inactive. The dimers were lacking a hexapeptide at the N-terminus; however, the secondary structure was the same as that of native lactate dehydrogenase. The circular dichroism spectra showed a dependence on temperature which suggested an equilibrium of two different structural states.The reaction of antibodies against native porcine heart LDH with the dimers restored the catalytic activity, and subsequently the dimers behaved similarly to the native enzyme. Addition of 1 M phosphate or NAD-sulfite to the dimers restored 80–90% of the catalytic activity. It could be demonstrated that the behaviour of the reactivated dimers, in contrast to that of the inactive dimers, was similar to the behaviour of native lactate dehydrogenase. For instance, ultracentrifugal analysis showed that dimers reactivated with NAD–SO₃ ^– were associated to give tetramers.The reaction of antibodies against native LDH with the dimers reactivated with NAD–SO ₃ ^– demonstrated that the native LDH and the dimers have the same surface determinants.     

调节己糖磷酸途径提高被孢霉花生四烯酸产量

研究了己糖单磷酸途径在被孢霉生产花生四烯酸中的作用。对被孢霉中己糖单磷酸途径的关键酶－葡萄糖－6－磷酸脱氢酶（G6PDH）活性的变化与生物量、油脂和花生四烯酸合成的关系进行了分析,结果表明在被孢霉发酵生产花生四烯酸的过程中,G6PDH活性的变化与生物量、总油脂产量、花生四烯酸含量及产量成正相关。利用0．8g/L谷氨酸对G6PDH进行正调节,可进一步提高被孢霉生物量、总油脂产量、花生四烯酸含量及产量。     

Separation and Purification of Betaine Aldehyde Dehydrogenase from Wild Suaeda liaotungensis

High active betaine aldehyde dehydrogenase (BADH,EC1.2.1.8) is found in wild Suaeda liaotungensis.The enzyme is purified 206-fold with recovery of 1.5%,It have a spectific activity of 2363 nmol/min.mg protein and the molecular mass of each subunit is 64.5kDa as determined by SDS-PAGE.     

青海湖裸鲤和鲤鱼组织乳酸脱氢酶同工酶比较研究

采用聚丙烯酰胺凝胶电泳法(PAGE)对青海湖裸鲤和鲤鱼的血清及组织乳酸脱氢酶(LDH)同工酶进行了比较研究。结果表明,青海湖裸鲤的血清及组织LDH共表现出LDHF4、LDHA4、LDHA2B2、LDHB4和LDHE4 5种主要同工酶,而鲤鱼共表现出LDHF4、LDHA4、LDHA2B2和LDHB4 4种主要同工酶,并且LDH同工酶在种间和种内不同组织中均表现出分布特异性。     

壳聚糖类植物保养剂对玉米根生理作用初探

使用不同浓度的壳聚糖、羧甲基壳聚糖及因子A对玉米进行浸种实验,发现适当浓度的壳聚糖类物质及因子A单独及复合均可提高苗期玉米根的重量、吸收面积和脱氢酶活性。其提高作用随壳聚糖及其衍生物和因子A等不同和浓度变化而不同。在单因子实验中,0．01％～0．025％的壳聚糖类物质和0．001％的因子A对玉米根活力有较好的促进作用。在单因子实验结果基础上初步形成了“复方植物保养剂”的几种不同配方,并对该配方进行实验,得到比单纯壳聚糖类物质及因子A促进效果更好的最佳配方为0．001％因子A加上0．01％的壳聚糖和0．01％的脱乙羧基壳聚糖,其可提高玉米根干重的61．1％,活跃吸收面积的37．20％和脱氢酶的80．82％。     

螺旋升流式反应器系统中污泥特性

螺旋升流式反应器是一种新的污水处理工艺,该反应器具有很好的对COD、TP、TN等的处理效果。本文对螺旋升流式反应器在污水脱氮除磷处理中的污泥特性进行了分析,发现MLVSS／MLSS在厌氧单元中呈现递增变化趋势,在缺氧和好氧单元呈现递减变化趋势,这种变化趋势在脱氮除磷效果好时明显,不好时不明显。镜检发现反应器中微生物丰富多样,颗粒污泥紧密、结实。污泥的SV在10％～18％,SVI在30～70之间。污泥的耗氧呼吸速率SOUR随厌氧过程逐渐升高,好氧过程逐渐降低：脱氢酶活性却表现出与之相反的变化规律。     

枯草杆菌6-磷酸葡萄糖酸脱氢酶的分离纯化及部分性质研究

采用DEAE—Sephaurose离子交换层析,Blue-Seplaarose CL-6B特异结合层析和Sephadex G-200凝胶过滤技术,对枯草芽孢杆菌中的6-磷酸葡萄糖酸脱氢酶进行了分离纯化,纯化倍数为112．3倍,比活为1．46U／mg,回收率为8．2％,纯化酶液经聚丙烯酰胺凝胶电泳检验为单一带,测得全酶相对分子质量为107kD,具有两个分子量相同的亚基,亚基相对分子质量为51kD,最适pH值为8．0,最适温度为30℃,对热不稳定,以6-磷酸葡萄糖酸和NADP^ 为底物,其Km值分别为Km1(NADP^ )=19．8μmol／L和Km2(6-GPA)=22．6μmol／L,在5mmol／L～50mmol／L浓度范围内,Mg^ ,Ca^2 和Mn^2 对酶有激活作用,Fe^3 和Cu^2 对酶有抑制作用,K^ ,Na^ ,Cl^-,NO^-3,SO^-4对酶几乎没有影响,用PMSF,TNBS,NBS,DTT和BrAc对酶进行修饰,实验结果表明,丝氨酸、苏氨酸、赖氨酸和组氨酸残基可能是该酶活性中心的功能基团。     

Experimental data on the energetic flux during glycolytic oscillations in yeast extracts

Calorimetric experiments were performed on yeast extracts in which glycolytic oscillations were occurring. High metabolic fluxes coincided with low amplitudes and with high frequencies in a temperature range from 283 to 303 K, yielding an activation energy ofE _a=76.8 kJ mol^–1 and a mean Q₁₀ value of 2.5±0.4. The calorimetrically determined reaction enthalpy _fH^0, of the glycolytic catabolism of glucose revealed two distinct groups of extract preparations, with no intermediate values. The values were –107.5±28.7 kJ mol^–1 and –30.8±5.7 kJmol^–1, respectively, while –100.0 kJ mol^–1 was predicted from theoretical calculations. Kreuzberg and Betz⁶ predicted rate limiting effects of GAPDH in oscillating extracts. However, when possible effects of GAPDH on frequency, number of oscillations or total heat production were examined, no influence of increasing or reducing the initial GAPDH concentration could be found. The results are discussed with reference to existing models of glycolytic oscillations.     

罗卜（Raphanus sativus L．）雄性不育系小孢子发生中的酶细胞化学初探

采用酶细胞化学技术探讨了萝卜雄性不育系６４Ａ小孢子发生不同阶段中琥珀酸脱氢酶（ＳＤＨ）的定位及其活性的变化情况．结果表明ＳＤＨ活性反应物主要分布于线粒体的内膜和嵴．保持系６４Ｂ小孢子发生过程中，线粒体的ＳＤＨ反应一直存在，随着小孢子发育其活性还有所增强．在不育系中，单核早期小孢子的线粒体ＳＤＨ活性较明显；单核晚期时小孢子内线粒体减少，其ＳＤＨ活性也渐弱．以后，小孢子的发育受阻，以致相当于二胞花粉时期的不育系花药内已无花粉．     

Involvement of a cytoplasmic glyceraldehyde-3- phosphate dehydrogenase GapC-2 in low-phosphate- induced anthocyanin accumulation in Arabidopsis

Phosphorous is one of the essential mineral elements for plant growth and development.Typically, the shoots of plant seedlings usually turn a dark-brown or purple colour under low-Pi stress. Using protein 2-D gel and peptide mass fingerprinting mapping (PMF) methods, a cytoplasmic glyceralde-hyde-3-phosphate dehydrogenase GapC-2 was identified as a low-Pi responsive protein in Arabidopsisplants. Expression of AtGapC-2 protein was significantly decreased after 4 d of low-Pi stress. Two in-dependent T-DNA insertion lines of GapC-2 gene (At1g13440) showed a hypersensitive phenotype inresponse to low-Pi stress compared with wild type plants, while the transgenic complementation linesof the mutants showed a similar phenotype to the wild type. These results indicate that AtGapC-2 mayplay an important role in Arabidopsis responses to low-Pi stress, possibly by regulation of glycoly-sis-associated "Pi-pool" and accumulation of anthocyanin pigments in plants.