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Oxidative aliphatic carbon-carbon bond cleavage reactions

COORDINATION CHEMISTRY REVIEWS 2013年第21-22期257卷 3005-3029页

作者： Allpress, Caleb J. Berreau, Lisa M. Utah State Univ Dept Chem & Biochem Logan UT 84322 USA

Over the past decade, several metalloenzymes have been characterized which catalyze dioxygenase-type aliphatic carbon-carbon bond cleavage reactions. The substrates for these enzymes vary from species that are stable with respect to O-2 under ambient conditions, to examples that in anionic form exhibit O-2 reactivity in the absence of enzyme. Described herein are advances from studies of the enzymes themselves and model systems. These combined investigations provide insight into novel mechanistic pathways leading to aliphatic carbon-carbon bond cleavage and/or the factors that influence regioselectivity in the oxidative carbon-carbon bond cleavage reactions. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Dioxygen activation Bioinorganic chemistry Dioxygenase Enzyme catalysis Carbon monoxide structure-function relationships

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Characterization of a multifunctional α2,3-sialyltransferase from Pasteurella dagmatis

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GLYCOBIOLOGY 2013年第11期23卷 1293-1304页

作者： Schmoelzer, Katharina Ribitsch, Doris Czabany, Tibor Luley-Goedl, Christiane Kokot, Deja Lyskowski, Andrzej Zitzenbacher, Sabine Schwab, Helmut Nidetzky, Bernd Austrian Ctr Ind Biotechnol A-8010 Graz Austria Graz Univ Technol Inst Biotechnol & Biochem Engn A-8010 Graz Austria Graz Univ Technol Inst Mol Biotechnol A-8010 Graz Austria

A new multifunctional alpha 2,3-sialyltransferase has been discovered in Pasteurella dagmatis. The enzyme, in short PdST, was identified from the P. dagmatis genome by sequence similarity with sialyltransferases of glycosyltransferase family GT-80. In addition to its regioselective sialyltransferase activity (5.9 U/mg;pH 8.0), purified PdST is alternatively active at low pH as alpha 2,3-sialidase (0.5 U/mg;pH 4.5) and alpha 2,3-trans-sialidase (1.0 U/mg;pH 4.5). It also shows cytidine-5'-monophosphate N-acetyl-neuraminic (CMP-Neu5Ac) hydrolase activity (3.7 U/mg;pH 8.0) when no sialyl acceptor substrate is present in the reaction. After sialyltransferase PmST1 from P. multocida, PdST is the second member of family GT-80 to display this remarkable catalytic promiscuity. A unique feature of PdST, however, is a naturally occurring Ser-to-Thr substitution within a highly conserved Y(112)DDGS(116) sequence motif. In PmST1, the equivalent Ser(143) is involved in binding of the CMP-Neu5Ac donor substrate. Reversion of the natural mutation in a T116S-PdST variant resulted in a marked increase in alpha 2,3-trans-sialidase side activity (4.0 U/mg;pH 4.5), whereas the major sialyltransferase activity was lowered (3.8 U/mg;pH 8.0). The Michaelis-Menten constant for CMP-Neu5Ac was decreased 4-fold in T116S mutant when compared with wild-type PdST (K-M=1.1 mM), indicating that residue 116 of PdST contributes to a delicate balance between substrate binding and catalytic activity. D-Galactose and various beta-D-galactosides function as sialyl acceptors from CMP-Neu5Ac, whereas other hexoses (e. g. D-glucose) are inactive. structure comparison was used to rationalize the particular acceptor substrate specificity of PdST in relation to other GT-80 sialyltransferases that show strict alpha 2,3-regioselectivity, but are flexible in using alpha/beta-galactosides for sialylation.

关键词： bacterial sialyltransferase glycosyltransferase family GT-80 natural mutation N-terminal elongation structure-function relationships

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Biomineralization proteins： from vertebrates to bacteria

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Frontiers in Biology 2013年第2期8卷 234-246页

作者： Lijun WANG Marit NILSEN-HAMILTON Ames Laboratory U. S. Department of Energy Department of Biochemistry Biophysics and Molecular Biology Iowa State University AmesIA 50011 USA

Biomineralization processes are frequently found in nature. Living organisms use various strategies to create highly ordered and hierarchical mineral structures under physiologic conditions in which the temperatures and pressures are much lower than those required to form the same mineralized structures by chemical synthesis. Although the mechanism of biomineralization remains elusive, proteins have been found responsible for the formation of such mineral structures in many cases. These proteins are active components in the process of biomineralization. The mechanisms by which their function can vary from providing active organic matrices that control the formation of specific mineral structures to being catalysts that facilitate the crystallization of certain metal ions. This review summarizes the current understanding of the functions of several representative biomineralization proteins from vertebrates to bacteria in the hopes of providing useful insight and guidance for further elucidation of mechanisms of biomineralization processes in living organisms.

关键词： biomineralization proteins structure-function relationships self-assembly nanoparticles

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Is the Link between Anatomical structure and function Equally Strong at All Cognitive Levels of Processing?

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CEREBRAL CORTEX 2012年第7期22卷 1593-1603页

作者： Tahmasebi, Amir M. Davis, Matthew H. Wild, Conor J. Rodd, Jennifer M. Hakyemez, Helene Abolmaesumi, P. Johnsrude, Ingrid S. Baycrest Ctr Geriatr Care Rotman Res Inst Toronto ON M6A 2E1 Canada MRC Cognit & Brain Sci Unit Cambridge CB2 2EF England Queens Univ Ctr Neurosci Studies Kingston ON K7L 3N6 Canada UCL Dept Cognit Perceptual & Brain Sci London WC1H 0AP England Queens Univ Dept Psychol Kingston ON K7L 3N6 Canada Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada Linkoping Univ Linnaeus Ctr Hearing & Deafness SE-58183 Linkoping Sweden

Whereas low-level sensory processes can be linked to macroanatomy with great confidence, the degree to which high-level cognitive processes map onto anatomy is less clear. If function respects anatomy, more accurate intersubject anatomical registration should result in better functional alignment. Here, we use auditory functional magnetic resonance imaging and compare the effectiveness of affine and nonlinear registration methods for aligning anatomy and functional activation across subjects. Anatomical alignment was measured using normalized cross-correlation within functionally defined regions of interest. functional overlap was assessed using t-statistics from the group analyses and the degree to which group statistics predict high and consistent signal change in individual data sets. In regions related to early stages of auditory processing, nonlinear registration resulted in more accurate anatomical registration and stronger functional overlap among subjects compared with affine. In frontal and temporal areas reflecting high-level processing of linguistic meaning, nonlinear registration also improved the accuracy of anatomical registration. However, functional overlap across subjects was not enhanced in these regions. Therefore, functional organization, relative to anatomy, is more variable in the frontal and temporal areas supporting meaning-based processes than in areas devoted to sensory/perceptual auditory processing. This demonstrates for the first time that functional variability increases systematically between regions supporting lower and higher cognitive processes.

关键词： anatomy fMRI functional variability hearing image normalization language lexical ambiguity semantic processing speech perception structure-function relationships

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Identification of functional elements of the GDP-fucose transporter SLC35C1 using a novel Chinese hamster ovary mutant

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GLYCOBIOLOGY 2012年第7期22卷 897-911页

作者： Zhang, Peiqing Haryadi, Ryan Chan, Kah Fai Teo, Gavin Goh, John Pereira, Natasha Ann Feng, Huatao Song, Zhiwei ASTAR Bioproc Technol Inst Singapore 138668 Singapore Natl Univ Singapore Dept Biochem Singapore 119077 Singapore

The GDP-fucose transporter SLC35C1 critically regulates the fucosylation of glycans. Elucidation of its structure-function relationships remains a challenge due to the lack of an appropriate mutant cell line. Here we report a novel Chinese hamster ovary (CHO) mutant, CHO-gmt5, generated by the zinc-finger nuclease technology, in which the Slc35c1 gene was knocked out from a previously reported CHO mutant that has a dysfunctional CMP-sialic acid transporter (CST) gene (Slc35a1). Consequently, CHO-gmt5 harbors double genetic defects in Slc35a1 and Slc35c1 and produces N-glycans deficient in both sialic acid and fucose. The structure-function relationships of SLC35C1 were studied using CHO-gmt5 cells. In contrast to the CST and UDP-galactose transporter, the C-terminal tail of SLC35C1 is not required for its Golgi localization but is essential for generating glycans that are recognized by a fucose-binding lectin, Aleuria aurantia lectin (AAL), suggesting an important role in the transport activity of SLC35C1. Furthermore, we found that this impact can be independently contributed by a cluster of three lysine residues and a Glu-Met (EM) sequence within the C terminus. We also showed that the conserved glycine residues at positions 180 and 277 of SLC35C1 have significant impacts on AAL binding to CHO-gmt5 cells, suggesting that these conserved glycine residues are required for the transport activity of Slc35 proteins. The absence of sialic acid and fucose on Fc N-glycan has been independently shown to enhance the antibody-dependent cellular cytotoxicity (ADCC) effect. By combining these features into one cell line, we postulate that CHO-gmt5 may represent a more advantageous cell line for the production of recombinant antibodies with enhanced ADCC effect.

关键词： GDP-fucose transporter glycosylation mutant protein fucosylation structure-function relationships zinc-finger nucleases

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structure-Activity relationships of α-, β₁-, γ-, and δ-Tomatine and Tomatidine against Human Breast (MDA-MB-231), Gastric (KATO-III), and Prostate (PC3) Cancer Cells

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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2012年第15期60卷 3891-3899页

作者： Choi, Suk Hyun Ahn, Jun-Bae Kozukue, Nobuyuki Kim, Hyun-Jeong Nishitani, Yosuke Zhang, Ling Mizuno, Masashi Levin, Carol E. Friedman, Mendel ARS Western Reg Res Ctr USDA Albany CA 94710 USA Seowon Univ Dept Food Serv Ind Cheongju 361742 South Korea Seowon Univ Bio Organ Mat & Food Ctr Cheongju 361742 South Korea Keimyung Univ Ctr Tradit Microorganism Resources Taegu 704701 South Korea Kobe Univ Org Adv Sci & Technol Team Hlth Biosci Kobe Hyogo 6578501 Japan Kobe Univ Dept Agrobiosci Grad Sch Agr Sci Kobe Hyogo 6578501 Japan

Partial acid hydrolysis of the tetrasaccharide (lycotetraose) side chain of the tomato glycoalkaloid alpha-tomatine resulted in the formation of four products with three, two, one, and zero carbohydrate side chains, which were separated by high-performance liquid chromatography (HPLC) and identified by thin-layer chromatography (TLC) and liquid chromatography ion-trap time-of-flight mass spectrometry (LCMS-IT-TOF). The inhibitory activities in terms of IC50 values (concentration that inhibits 50% of the cells under the test conditions) of the parent compound and the hydrolysates, isolated by preparative HPLC, against normal human liver and lung cells and human breast, gastric, and prostate cancer cells indicate that (a) the removal of sugars significantly reduced the concentration-dependent cell-inhibiting effects of the test compounds, (b) PC3 prostate cancer cells were about 10 times more susceptible to inhibition by alpha-tomatine than the breast and gastric cancer cells or the normal cells, (c) the activity of alpha-tomatine against the prostate cancer cells was 200 times greater than that of the aglycone tomatidine, and (d) the activity increased as the number of sugars on the aglycone increased, but this was only statistically significant at p < 0.05 for the normal lung He1299 cell line. The effect of the alkaloids on tumor necrosis factor alpha (TNF-alpha) was measured in RAW264.7 macrophage cells. There was a statistically significant negative correlation between the dosage of gamma- and alpha-tomatine and the level of TNF-alpha. alpha-Tomatine was the most effective compound at reducing TNF-alpha. The dietary significance of the results and future research needs are discussed.

关键词： Tomatoes alpha-tomatine hydrolysis TLC mass spectrometry cancer cells inhibition tumor necrosis factor alpha structure-function relationships mechanisms

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Synthetic polyamines as potential amine oxidase inhibitors: a preliminary study

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AMINO ACIDS 2012年第2-3期42卷 913-928页

作者： Bonaiuto, Emanuela Minarini, Anna Tumiatti, Vincenzo Milelli, Andrea Lunelli, Michele Pegoraro, Maurizio Rizzoli, Valeria Di Paolo, Maria Luisa Univ Padua Dept Biol Chem I-35131 Padua Italy Alma Mater Studiorum Univ Bologna Dept Pharmaceut Sci I-40126 Bologna Italy Max Planck Inst Infect Biol Dept Cellular Microbiol D-10117 Berlin Germany San Bortolo Hosp Dept Plast Surg I-36100 Vicenza Italy Consorzio Interuniv Ist Nazl Biostrutture & Biosi I-00136 Rome Italy

In the last few decades, medicinal chemists have carried out extensive research on synthetic polyamines for use as anticancer drugs and multitarget-directed ligands in neurodegenerative diseases. The aim of this study was to evaluate the effect of some synthetic polyamines as inhibitors of two new potential targets, human semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) and monoamine oxidases B (MAO B), enzymes involved in various multi-factorial diseases such as Alzheimer's disease. N,N'-Dibenzyl-dodecane-1,12-diamine (Bis-Bza-Diado), a newly synthesised compound, and ELP 12, a muscarinic cholinergic M-2 receptor antagonist, were found to behave as reversible and mixed non-competitive inhibitors of both amine oxidases (dissociation constants of about 100 mu M). ELP 12 was found to be more selective for SSAO/VAP-1. Combining kinetic and structural approaches, the binding mode of ELP 12 to SSAO/VAP-1 was investigated. ELP 12 may bind at the entrance of the active site channel by ionic interactions with ASP446 and/or ASP180;one end of the polyamine may be accommodated inside the channel, reaching the TPQ cofactor area. The binding of ELP 12 induces rearrangement of the secondary structure of the enzyme and impedes substrate entry and/or product release and catalysis. These structural data reveal that the entrance and the first part of the SSAO/VAP-1 channel may be considered as a new target area, or a "secondary binding site", for modulators of human SSAO/VAP-1 activity. These results indicate ELP 12 and Bis-Bza-Diado as new "skeletons" for the development of novel SSAO/VAP-1 and MAO B inhibitors.

关键词： Synthetic polyamines Semicarbazide-sensitive amine oxidases Monoamine oxidase B Amine oxidase inhibitors structure-function relationships

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functional Determinants of Temperature Adaptation in Enzymes of Cold- versus Warm-Adapted Mussels (Genus Mytilus)

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MOLECULAR BIOLOGY AND EVOLUTION 2012年第10期29卷 3061-3070页

作者： Lockwood, Brent L. Somero, George N. Stanford Univ Hopkins Marine Stn Stanford CA 94305 USA

Temperature is a strong selective force on the evolution of proteins due to its effects on higher orders of protein structure and, thereby, on critical protein functions like ligand binding and catalysis. Comparisons among orthologous proteins from differently thermally adapted species show consistent patterns of adaptive variation in function, but few studies have examined functional adaptation among multiple structural families of proteins. Thus, with our present state of knowledge, it is difficult to predict what fraction of the proteome will exhibit adaptive variation in the face of temperature increases of a few to several degrees Celsius, that is, temperature increases of the magnitude predicted by models of global warming. Here, we compared orthologous enzymes of the warm-adapted Mediterranean mussel Mytilus galloprovincialis and the cold-adapted Mytilus trossulus, a native of the North Pacific Ocean, species whose physiologies exhibit significantly different responses to temperature. We measured the effects of temperature on the kinetics (Michaelis-Menten constant-K-m) of five enzymes that are important for ATP generation and that represent distinct protein structural families. Among phosphoglucomutase (PGM), phosphoglucose isomerase (PGI), pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (GTP) (PEPCK), and isocitrate dehydrogenase (NADP) (IDH), only IDH orthologs showed significantly different thermal responses of K-m between the two species. The K-m of isocitrate of M. galloprovincialis-IDH was intrinsically lower and more thermally stable than that of M. trossulus-IDH and thus had higher substrate affinity at high temperatures. Two amino acid substitutions account for the functional differences between IDH orthologs, one of which allows for more hydrogen bonds to form near the mobile region of the active site in M. galloprovincialis-IDH. Taken together, our findings cast light on the targets of adaptive evolution in the context of climate change;on

关键词： adaptation invasive species Michaelis-Menten constants (K-m) Mytilus protein evolution structure-function relationships temperature

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Biological parametric mapping accounting for random regressors with regression calibration and model II regression

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NEUROIMAGE 2012年第3期62卷 1761-1768页

作者： Yang, Xue Lauzon, Carolyn B. Crainiceanu, Ciprian Caffo, Brian Resnick, Susan M. Landman, Bennett A. Vanderbilt Univ Nashville TN 37235 USA NIA NIH Baltimore MD 21224 USA Johns Hopkins Univ Sch Publ Hlth Baltimore MD 21218 USA Johns Hopkins Univ Baltimore MD 21205 USA

Massively univariate regression and inference in the form of statistical parametric mapping have transformed the way in which multi-dimensional imaging data are studied. In functional and structural neuroimaging, the de facto standard "design matrix"-based general linear regression model and its multi-level cousins have enabled investigation of the biological basis of the human brain. With modem study designs, it is possible to acquire multi-modal three-dimensional assessments of the same individuals-e.g., structural, functional and quantitative magnetic resonance imaging, alongside functional and ligand binding maps with positron emission tomography. Largely, current statistical methods in the imaging community assume that the regressors are non-random. For more realistic multi-parametric assessment (e.g., voxel-wise modeling), distributional consideration of all observations is appropriate. Herein, we discuss two unified regression and inference approaches, model II regression and regression calibration, for use in massively univariate inference with imaging data. These methods use the design matrix paradigm and account for both random and non-random imaging regressors. We characterize these methods in simulation and illustrate their use on an empirical dataset. Both methods have been made readily available as a toolbox plug-in for the SPM software. (c) 2012 Elsevier Inc. All rights reserved.

关键词： structure-function relationships Random regressors Regression calibration Model II regression General linear model

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Cardiotoxin-I: An Unexpectedly Potent Insulinotropic Agent

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CHEMBIOCHEM 2012年第12期13卷 1805-1812页

作者： Thi Tuyet Nhung Nguyen Folch, Benjamin Letourneau, Myriam Vaudry, David Nam Hai Truong Doucet, Nicolas Chatenet, David Fournier, Alain Univ Quebec INRS Inst Armand Frappier Laval PQ H7V 1B7 Canada Inst Biotechnol Hanoi Vietnam Univ Rouen IFRMP 23 F-76821 Mont St Aignan France Univ Rouen INRS INSERM Lab Int Associe Samuel de Champlain F-76821 Mont St Aignan France

Insulin secretion from pancreatic beta-cells is a complex process, involving the integration and interaction of multiple external and internal stimuli, in which glucose plays a major role. Understanding the physiology leading to insulin release is a crucial step toward the identification of new targets. In this study, we evaluated the presence of insulinotropic metabolites in Naja kaouthia snake venom. Only one fraction, identified as cardiotoxin-I (CTX-I) was able to induce insulin secretion from INS-1E cells without affecting cell viability and integrity, as assessed by MTT and LDH assays. Interestingly, CTX-I was also able to stimulate insulin secretion from INS-1E cells even in the absence of glucose. Although cardiotoxins have been characterized as potent hemolytic agents and vasoconstrictors, CTX-I was unable to induce direct hemolysis of human erythrocytes or to induce potent vasoconstriction. As such, this newly identified insulin-releasing toxin will surely enrich the pool of existing tools to study beta-cell physiology or even open a new therapeutic avenue.

关键词： cardiotoxin-I insulin ion channels peptides structure-function relationships

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