Branched-chain alpha-keto acid dehydrogenase kinase content in rat skeletal muscle is decreased by endurance training

The activity state of branched-chain alpha-keto acid dehydrogenase complex in skeletal muscle was elevated by running exercise in trained and untrained rats, but level of this elevation was significantly greater in the former than in the latter. To elucidate the mechanism of the training effect on the exercise-induced activation of the complex, a protein amount of branched-chain alpha-keto acid dehydrogenase kinase, which is responsible for inactivation of the complex by phosphorylation, in the muscle was measured by the Western blot analysis. Endurance training decreased the content of the kinase protein in the muscle by approximately 30%, suggesting that this decrease is involved in the mechanisms for greater activation of the complex by exercise in trained rats.     

Studies on the activation and inactivation of the branched chain alpha-keto acid dehydrogenase in the perfused rat heart

Evidence for a reversible process resulting in stable activated and inactivated states of the mitochondrial branched chain alpha-keto acid dehydrogenase complex in isolated perfused rat heart is presented. The inactivation process is mediated by pyruvate infusion, while activation (up to 18-fold) is facilitated by branched chain alpha-keto acid substrates. The low activity state of the branched chain complex characteristic of freshly excised rat hearts could be maintained by infusion of either pyruvate or glucose. Activation of the complex in the perfused rat heart was achieved slowly by substrate-free perfusion, while rapid activation was accomplished by infusion of branched chain alpha-keto acids. The fully activated enzyme complex resulting from branched chain alpha-keto acid infusion subsequently could be inactivated maximally by infusion of pyruvate alone or intermediate degrees of inactivation could be produced by certain ratios of co-infused pyruvate and branched chain alpha-keto acid. alpha-Ketoisocaproate was an order of magnitude more effective than alpha-keto isovalerate either in preventing inactivation or in stimulating the opposing activation process when co-infused with pyruvate. The mitochondrial pyruvate transport inhibitor, alpha-cyanocinnamate, effectively prevented inactivation of the complex by infused pyruvate. Differential changes in the activation states of the branched chain alpha-keto acid dehydrogenase and pyruvate dehydrogenase complexes were evident when the two complexes were compared in apparently similar flux-inhibited (via octanoate infusion) and flux-stimulated (via dichloroacetate infusion) metabolic conditions. The differential effect of pyruvate concentration on the activity states of the two complexes was also well-defined. The results of the present study suggest distinct systems for the regulation of the activity of the two multienzyme complexes of interest. While our results argue neither for nor against an inactivation of the branched chain alpha-keto acid dehydrogenase complex by a protein kinase, the regulatory properties of such an intramitochondrial protein kinase may not be similar to the pyruvate dehydrogenase kinase. The mechanistic nature of the suggested novel regulatory system concerned with the pyruvate-mediated inactivation of the branched chain alpha-keto acid activation cannot be inferred at the present time.     

Microbial models of soil metabolism: biotransformations of danofloxacin

Danofloxacin is a new synthetic fluoroquinolone antibacterial agent under development for exclusive use in veterinary medicine. Such use could lead to deposition of low levels of danofloxacin residues in the environment in manure from treated livestock. This study was conducted to evaluate the potential for indigenous soil microorganisms to metabolize danofloxacin. Cultures of 72 soil microorganisms representing a diverse panel of bacteria, fungi and yeast were incubated with danofloxacin mesylate substrate and samples analyzed periodically by high performance liquid chromatography for loss of danofloxacin and formation of metabolites. Some samples were further analyzed by liquid chromatography-mass spectrometry and mass spectrometry to confirm metabolite identification. Twelve organisms, representing eight different genera, biotransformed danofloxacin to metabolites detectable by the chromatographic methods employed. Two Mycobacterium species, two Pseudomonas species, and isolates of Nocardia sp, Rhizopus arrhizus and Streptomyces griseus all formed N-desmethyldanofloxacin. The formation of the 7-amino danofloxacin derivative, 1-cyclopropyl-6-fluoro-7-amino-4-oxo-1,4-dihydroquinoline-3-carboxylic acid by cultures of Candida lipopytica, Pseudomonas fluorescens, two Mycobacterium species and three Penicillium species demonstrates the propensities of these cultures to completely degrade the piperazine ring. At least two additional and unidentified metabolite peaks were observed in chromatograms of Aspergillus nidulans and Penicillium sp cultures. Radiolabled [2-14C]danofloxacin added to cultures of the fungus Curvularia lunata was apparently mineralized, with approximately 31% of the radiolabel recovered as volatile metabolites after 24 h of incubation, indicating the susceptibility of the quinolone ring to microbial metabolic degradation.     

Non-conventional enzyme catalysis: application of proteases and zymogens in biotransformations

One of the attractions of using enzymes for chemical syntheses is the control of stereochemistry: problems of racemization that attend chemical C-N ligation methods are completely avoided. Furthermore, the enzymatic approach has the advantage that only minimal protection-deprotection steps are involved. The Impetus to develop non-conventional catalysis procedures has sprung from the lack of usable native enzymes that normally catalyze the formation of peptide bonds for biotransformation. In peptide syntheses that make use of the 'reverse hydrolysis potential' of proteases several problems need to be considered, especially the necessity of minimizing competing hydrolysis of weakly activated acyl donor esters and the need to circumvent undesired product cleavage. Some approaches to suppress competitive reactions have been developed in our group, namely leaving group manipulations at the acyl donor in kinetically controlled reactions, enzymatic synthesis in organic solvent-free micro-aqueous systems, cryoenzymatic peptide synthesis, and biotransformations in frozen aqueous systems. Finally, for the first time, zymogens, which are known as catalytically inactive precursors of proteases, could be used as biocatalysts for practically irreversible peptide bond formation.     

Regulation of the cyanide-resistant alternative oxidase of plant mitochondria. Identification of the cysteine residue involved in alpha-keto acid stimulation and intersubunit disulfide bond formation

The cyanide-resistant alternative oxidase of plant mitochondria is a homodimeric protein whose activity can be regulated by a redox-sensitive intersubunit sulfhydryl/disulfide system and by alpha-keto acids. After determining that the Arabidopsis alternative oxidase possesses the redox-sensitive sulfhydryl/disulfide system, site-directed mutagenesis of an Arabidopsis cDNA clone was used to individually change the two conserved Cys residues, Cys-128 and Cys-78, to Ala. Using diamide oxidation and chemical cross-linking of the protein expressed in Escherichia coli, Cys-78 was shown to be: 1) the Cys residue involved in the sulfhydryl/disulfide system; and 2) not required for subunit dimerization. The C128A mutant was stimulated by pyruvate, while the C78A mutant protein had little activity and displayed no stimulation by pyruvate. Mutating Cys-78 to Glu produced an active enzyme which was insensitive to pyruvate, consistent with alpha-keto acid activation occurring through a thiohemiacetal. These results indicate that Cys-78 serves as both the regulatory sulfhydryl/disulfide and the site of activation by alpha-keto acids. In light of these results, the previously observed effects of sulfhydryl reagents on the alternative oxidase of isolated soybean mitochondria were re-examined and were found to be in agreement with a single sulfhydryl residue being the site both of alpha-keto acid activation and of the regulatory sulfhydryl/disulfide system.     

HAZOP分析在硫磺制酸工程中的应用

概述了危险源及可操作性分析方法（HAZOP）,介绍了硫磺制酸工程的主要生产工艺,论述了硫磺制酸工程的HAZOP分析流程.硫磺制酸工程通过实施HAZOP分析,减少了详细设计错误,提高了自控系统的稳定性,保证了装置生产运行的安全性和可靠性.     

过滤器在稀酸净化固液分离中的应用

介绍了CNⅡ-3300型过滤器工作原理、结构、工艺流程和试用情况。针对有色冶炼烟气制酸净化中的含尘废酸，采用CN过滤器替代传统的沉降槽进行固液分离，效果好，运行成本低，上清液循环使用，减少了环境污染：     

High resolution crystal structure of pyruvate decarboxylase from Zymomonas mobilis. Implications for substrate activation in pyruvate decarboxylases

The crystal structure of tetrameric pyruvate decarboxylase from Zymomonas mobilis has been determined at 1.9 A resolution and refined to a crystallographic R-factor of 16.2% and Rfree of 19.7%. The subunit consists of three domains, all of the alpha/beta type. Two of the subunits form a tight dimer with an extensive interface area. The thiamin diphosphate binding site is located at the subunit-subunit interface, and the cofactor, bound in the V conformation, interacts with residues from the N-terminal domain of one subunit and the C-terminal domain of the second subunit. The 2-fold symmetry generates the second thiamin diphosphate binding site in the dimer. Two of the dimers form a tightly packed tetramer with pseudo 222 symmetry. The interface area between the dimers is much larger in pyruvate decarboxylase from Z. mobilis than in the yeast enzyme, and structural differences in these parts result in a completely different packing of the subunits in the two enzymes. In contrast to other pyruvate decarboxylases, the enzyme from Z. mobilis is not subject to allosteric activation by the substrate. The tight packing of the dimers in the tetramer prevents large rearrangements in the quaternary structure as seen in the yeast enzyme and locks the enzyme in an activated conformation. The architecture of the cofactor binding site and the active site is similar in the two enzymes. However, the x-ray analysis reveals subtle but significant structural differences in the active site that might be responsible for variations in the biochemical properties in these enzymes.     

酸洗缓蚀剂在钢铁生产中的应用研究

文章介绍了酸洗缓冲剂的作用机理，通过应用实验，研究了酸洗缓蚀剂的应用效果，并对几种常用缓蚀剂的作用效果进行了对比。结果表明，使用酸洗缓蚀剂可抑制酸雾挥发，防止钢材的过酸洗，减少钢材的酸洗耗量０．１３％，吨钢酸耗由２７．３ｋｇ／ｔ降到１５．９ｋｇ／ｔ，并能减少钢材在深加工过程中的氢脆现象，提高钢材的表面质量。     

浓硫酸混酸器在金隆工程中的应用

介绍金隆铜业有限公司铜冶炼烟气制酸系统干吸工序的不锈钢制新型结构形式的浓酸混酸器。该混酸器的特点是在管内混酸。该装置具有设计简单、结构合理，避免了传统混酸方式中存在的一些缺陷。     

硫酸盐还原菌在处理酸性矿山废水中的应用

利用硫酸盐还原菌(sulfate reducing bacteria, SRB)处理酸性矿山废水是目前研究的热点，在实际生产活动中有着非常广泛的应用.文章简要介绍酸性矿山废水的来源、特点及其危害，重点介绍SRB处理酸性矿山废水的机理，总结国内外SRB处理工艺在酸性矿山废水中的发展研究，并提出SRB处理酸性矿山废水方面存在的一些问题.      

Synthesis of optically active amino acids from alpha-keto acids with Escherichia coli cells expressing heterologous genes

We describe a simple method for enzymatic synthesis of L and D amino acids from alpha-keto acids with Escherichia coli cells which express heterologous genes. L-amino acids were produced with thermostable L-amino acid dehydrogenase and formate dehydrogenase (FDH) from alpha-keto acids and ammonium formate with only an intracellular pool of NAD+ for the regeneration of NADH. We constructed plasmids containing, in addition to the FDH gene, the genes for amino acid dehydrogenases, including i.e., leucine dehydrogenase, alanine dehydrogenase, and phenylalanine dehydrogenase. L-Leucine, L-valine, L-norvaline, L-methionine, L-phenylalanine, and L-tyrosine were synthesized with the recombinant E. coli cells with high chemical yields (> 80%) and high optical yields (up to 100% enantiomeric excess). Stereospecific conversion of various alpha-keto acids to D amino acids was also examined with recombinant E. coli cells containing a plasmid coding for the four heterologous genes of the thermostable enzymes D-amino acid aminotransferase, alanine racemase, L-alanine dehydrogenase, and FDH. Optically pure D enantiomers of glutamate and leucine were obtained.     

变色酸偶氮试剂在动力学光度分析中的应用

对变色酸偶氮试剂在催化动力学光度法测定过渡金属、贵金属及非金属含量方面的应用和速差动力学光度法测定混合稀土中单一稀土含量的方法进行了综述     

Transition-state theoretical interpretation of the catalytic power of pyruvate decarboxylases: the roles of static and dynamical considerations

Changes in marital and fertility behavior have influenced the role of father for many men. We use data from the first two waves of the National Survey of Families and Households to examine various sociodemographic, situational, and attitudinal characteristics that might influence the degree of contact between nonresidential fathers and their minor children. We tap two different dimensions of distance parenting and find that although several variables influence both visiting and talking on the telephone or writing letters, some factors (the presence of multiple children in a household) predict visiting only, while others (child's age and gender) predict only verbal/written contact. Similarly, some of the life-course decisions made by fathers appear to crowd out their involvement with nonresidential children, whereas other decisions reinforce their parenting behavior.     

磷酸在燃煤型塔式锌精馏炉砌筑中的应用

介绍了燃煤型锌精馏炉的基本炉型、耐火材料的选择及磷酸在筑炉中的应用.生产实践表明,添加适量的磷酸砌筑碳化硅塔盘,有利于延长塔体寿命.     

张力计在酸连轧轧机的应用及改进

介绍了太钢冷轧硅钢厂酸连轧机组张力计在轧机的测量原理及使用,以及在实际生产过程中张力计出现的不稳定性,故障率频发。为了确保张力计测量精度的稳定性,对张力计的故障点提出针对性改进措施,在使用过程中效果明显。     

低位高效干吸工艺技术在冶炼烟气制酸中应用

低位高效干吸工艺技术用于冶炼烟气干吸工序，技术稳妥可靠，较国内目前生产使用的干吸工艺有突出特点，生产运行稳定，技术指标好，占地面积少，节省建设投资和能耗。体现了硫酸工业的技术进步。     

Enzymatic reactions of methionine sulfoximine. Conversion to the corresponding alpha-imino and alpha-keto acids and to alpha-ketobutyrate and methane sulfinimide

L-Methionine sulfoximine is a substrate of L-amino acid oxidase (Crotalus adamanteus), glutamine transaminase, and gamma-cystathionase. In the reaction catalyzed by L-amino acid oxidase, methionine sulfoximine is converted to aplph-imino-gamma-methylsulfoximinylbutyrate, which undergoes rapid gamma elimination yielding methane sulfinimide and 2-imino-3-butenoic acid. Methane sulfinimide is converted to methane sulfonamide, methane sulfinic acid, and methane sulfonic acid; 2-imino-3-butenoic acid is hydrolyzed to vinylglyoxylate, which polymerizes to an insoluble product. When the reaction is carried out in the presence of semicarbazide, the imine formed initially is quantitatively trapped as alpha-keto-gamma-methylsulfoximinylbutyrate semicarbazone, from which the free alpha-keto acid may be obtained. When the reaction is carried out in the presence of a mercaptan (RSH), a gamma exchange reaction occurs leading to formation of a new alpha-keto acid substituted in the gamma position by an SR-group; thus, alpha-keto-gamma-(beta-hydroxyethiol)butyric acid (S-(hydroxyethyl)-2-keto-4-mercaptobutyric acid) was obtained when L-methionine sulfoximine was oxidized in the presence of 2-mercaptoethanol, and enzymatic transamination of this alpha-keto acid with L-glutamine gave the new amino acid, L-omega-hydroxyethionine. The reaction of L-methionine sulfoximine with gamma-cystathionase yields 1 mol each of alpha-ketobutyrate and methane sulfinimide; the latter is hydrolyzed almost exclusively to methane sulfinic acid. Transamination of L-methionine sulfoximine yields the corresponding alpha-keto acid (alpha-keto-gamma-methylsulfoximinylbutyrate), which is stable. Some of these reactions may occur in vivo, and thus contribute to the toxicity of L-methionine sulfoximine.     

二苯羟乙酸在痕量金的催化反应—示波极谱分析中的应用

在稀硫酸介质中及加热下，Ａｕ＾３＋对Ｃｅ＾４＋氧化Ｈｇ２＾２＋反应具有强烈催化作用；加入二苯羟乙酸以还原指示反应中未反应的Ｃｅ＾４＋，生成的二苯甲酮于－０．７８Ｖｖｓ。ＳＣＥ产生一灵敏的二阶导数波。据此，采用单扫描示波极谱法对催化测定金的各种影响因素进行了研究，建立了一个检出限和测定范围分别为０．２ｎｇ／ｍｌ和０．３８－７．７ｎｇ／ｍｌ金的催化反应—示波极谱分析新方法，已用于矿样中痕量金的测定。