Substrate specificity of the phosphorylated fructose-1,6-bisphosphatase dephosphorylating protein phosphatase from Saccharomyces cerevisiae

Enzymatic dephosphorylation of the phosphorylated forms of five different yeast enzymes has been studied: fructose-1,6-bisphosphatase, glycogen phosphorylase, neutral trehalase, NAD-glutamate dehydrogenase and 6-phosphofructo-2-kinase. Phosphorylated fructose-1,6-bisphosphatase and phosphorylated 6-phosphofructo-2-kinase were present in extracts of starved yeast cells which had been incubated for 10 min with glucose. Phosphorylated glycogen phosphorylase, neutral trehalase and NAD-glutamate dehydrogenase were obtained by incubation of yeast extract with ATP, cyclic AMP and Mg2+. After incubation with commercially available preparations of alkaline phosphatase, all five phosphorylated enzymes studied showed the changes in catalytic activity that would be expected as a consequence of dephosphorylation. The recently purified yeast enzyme which dephosphorylates phosphorylated fructose-1,6-bisophosphatase (Horn and Holzer (1987) however, was found to be active only with the phosphorylated fructose-1,6-bisphosphatase, but not with the other four phosphorylated enzymes studied. By contrast, a crude extract from yeast showed dephosphorylating activity towards all five substrates. Substrate specificity with the five phosphorylated enzymes studied of different phosphoprotein phosphatases from yeast prepared by others is discussed.     

Coherence and Specificity of Information-Processing Biases in Depression and Social Phobia.

Research has not resolved whether depression is associated with a distinct information-processing bias, whether the content of the information-processing bias in depression is specific to themes of loss and sadness, or whether biases are consistent across the tasks most commonly used to assess attention and memory processing. In the present study, participants diagnosed with major depression, social phobia, or no Axis I disorder, completed several information-processing tasks assessing attention and memory for sad, socially threatening, physically threatening, and positive stimuli. As predicted, depressed participants exhibited specific biases for stimuli connoting sadness; social phobic participants did not evidence such specificity for threat stimuli. It is important to note that the different measures of bias in memory and attention were not systematically intercorrelated. Implications for the study of cognitive bias in depression, and for cognitive theory more broadly, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A real time experimental setup for classification of epilepsy risk levels

The objective of this paper is to analyze the performance of singular value decomposition, expectation maximization, and Elman Neural Networks in optimization of code converter outputs in the classification of epilepsy risk levels from EEG (electroencephalogram) signals. The signal parameters such as the total number of positive and negative peaks, spikes and sharp waves, their duration etc., were extracted using morphological operators and wavelet transforms. Code converters were considered as a level one classifier. Code converters were found to have a performance index and quality value of 33.26 and 12.74, respectively, which is low. Consequently, for the EEG signals of 20 patients, the post classifiers were applied across 3 epochs of 16 channels. After having made a comparative study of different architectures, SVD was found to be the best post classifier as it marked a performance index of 89.48 and a quality value of 20.62. Elman neural network also exhibits good performance metrics than SVD in the morphological operator based feature extraction method.     

小分子配体模仿结合位点水分子: 相同配体与不同蛋白靶点之间作用模式的计算研究

在计算化学和药物设计领域中,精确预测小分子配体的蛋白质靶标是一件极具挑战性工作,特别是那些与相同小分子配体相互作用,但蛋白间并不具有显著序列或结构相似性的靶标蛋白。为了研究相同小分子配体与不相关的蛋白质靶标之间的结合特性,我们使用蛋白水合效应分析 (SPA) 程序研究了 33 对药物靶蛋白结合位点水分子的结构特性。每个蛋白对中的两个蛋白质,均由可与相同配体小分子相结合的两个不相关的蛋白质组成。通过计算两蛋白质间的水化位点替代重叠率,我们发现共有高达 73% 的蛋白对中有着显著的水分子替代重叠率值。特别是我们发现相同小分子与不同蛋白相互作用时,或许存在一种特别的“识别代码”,即小分子配体的功能基团与结合位点的水分子之间存在着较好的几何构型相似性。在无法确定小分子与蛋白相互作用模式时,可以依靠活性结合腔穴中水分子的结合构型特征,进行粗略估算与预测,对蛋白-配体相互作用模式研究有重要的实用价值。     

Selective hydrolysis of polyunsaturated fatty acid-containing oil withGeotrichum candidum lipase

Polyunsaturated fatty acids (PUFA), especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), can be concentrated in glycerides by hydrolyzing tuna oil withGeotrichum candidum lipase, the main components in the resulting oil being triglycerides. The reaction mechanism of this selective hydrolysis was investigated. Although the lipase acted well on the esters of oleic, linoleic, and α-linolenic acids, it did not affect the esters of γ-linolenic acid, arachidonic acid, EPA, and DHA as much. The action of PUFA-glycerides was mono-> di- > triglycerides. Furthermore, the condensation of PUFA-partial glycerides and PUFA occurred even in the presence of a large amount of water, and the partial glycerides converted to the triglycerides by transacylation. These results suggested that the PUFA-rich triglycerides were accumulated in the glyceride fraction by the following mechanism: The PUFA-partial glycerides generated by the hydrolysis were converted to PUFA-triglycerides by condensation and transacylation reactions. As the PUFA-triglycerides formed were the poor substrates of lipase, they were accumulated in the reaction mixture.     

Developmental stage of herbivorePseudaletia separata affects production of herbivore-induced synomone by corn plants

The female parasitic waspCotesia kariyai discriminated between the volatiles of corn leaves infested by younger host larvaePseudaletia separata (first to fourth instar) and uninfested leaves in a Y-tube olfactometer; the wasps were attracted to the infested leaves. In contrast, when corn plants were infested by the later stages (fifth and sixth instar) of the armyworm, the wasps did not distinguish between infested corn leaves and uninfested corn leaves in the olfactometer. Mechanically damaged leaves were no more attractive than undamaged leaves, and host larvae or their feces were not attractive to the parasitoid. Through chemical analysis, the herbivore-induced plant volatiles were identified in the headspace of infested corn leaves. The herbivore-induced volatiles (HIVs) constituted a larger proportion of the headspace of corn leaves infested by early instar armyworms than of corn leaves infested by late instar armyworms. Application of third-instar larval regurgitant onto artificially damaged sites of leaves resulted in emission of parasitoid attractants from the leaf, whereas leaves treated with sixth-instar regurgitant did not. The function of this herbivore-stage related specificity of herbivore-induced synomones is discussed in a tritrophic context.     

Cross-linked enzyme aggregates of recombinant cyclodextrin glycosyltransferase for high-purity β-cyclodextrin production

The cover image is based on the Research Article Cross-linked enzyme aggregates of recombinant cyclodextrin glycosyltransferase for high-purity β-cyclodextrin production by Jianguo Zhang et al., DOI: 10.1002/jctb.5912 .

     

Protein engineering of the relative specificity of glucoamylase from Aspergillus awamori based on sequence similarities between starch-degrading enzymes

Aspergillus glucoamylase catalyzes hydrolysis of D-glucose fromnon-reducing ends of starch with an {small tilde}300-fold {k^JKm) preference for the a-1,4- over the a-l,6-glucosidic linkagedetermined using the substrates maltose and iso-maltose. Itis postulated that as most amylolytic enzymes act on eitherthe a-1,4- or a-l,6-linkages, sequence comparison between active-siteregions should enable the correlation of the substrate bondspecificity with particular residues at key positions. Therefore,the already high bond-type selectivity in Aspergillus glucoamylasecould theoretically be augmented further by three single mutations,Serll9 Tyr, Glyl83 Lys and Serl84 His, in two separate active-siteregions. These mutants all had slight increases in activityas compared with the wild-type enzyme towards the a-l,4-linkedmaltose; this was due to lower Km values as well as small decreasesin activity towards isomaltose. This latter decrease in activitywas a result of higher Km values and a decrease in fc^, forthe Serl84 His mutant As a consequence, the selectivity of thethree glucoamylase mutants for a-1,4- over a-l,6-linked disaccharidesis enhanced 2.3- to 3.5-fold. In addition, the introductionof a cationic side chain in Glyl83 Lys and Serl84 His glucoamylase,broadens the optimal pH range for activity towards acidic aswell as alkaline conditions.