Plant mercaptopyruvate sulfurtransferases: molecular cloning, subcellular localization and enzymatic activities.

Mercaptopyruvate sulfurtransferase (MST, EC 2.8.1.2) and thiosulfate sulfurtransferase (TST, rhodanese, EC 2.8.1.1) are evolutionarily related enzymes that catalyze the transfer of sulfur ions from mercaptopyruvate and thiosulfate, respectively, to cyanide ions. We have isolated and characterized two cDNAs, AtMST1 and AtMST2, that are Arabidopsis homologs of TST and MST from other organisms. Deduced amino-acid sequences showed similarity to each other, although MST1 has a N-terminal extension of 57 amino acids containing a targeting sequence. MST1 and MST2 are located in mitochondria and cytoplasm, respectively, as shown by immunoblot analysis of subcellular fractions and by green fluorescent protein (GFP) analysis. However, some regions of MST1 fused to GFP were found to target not only mitochondria, but also chloroplasts, suggesting that the regions on the targeting sequence recognized by protein import systems of mitochondria and chloroplasts are not identical. Recombinant proteins, expressed in Escherichia coli, exhibited MST/TST activity ratios determined from kcat/Km values of 11 and 26 for MST1 and MST2, respectively. This indicates that the proteins encoded by both AtMST1 and AtMST2 are MST rather than TST type. One of the hypotheses proposed so far for the physiological function of MST and TST concerns iron-sulfur cluster assembly. In order to address this possibility, a T-DNA insertion Arabidopsis mutant, in which the AtMST1 was disrupted, was isolated by PCR screening of T-DNA mutant libraries. However, the mutation had no effect on levels of iron-sulfur enzyme activities, suggesting that MST1 is not directly involved in iron-sulfur cluster assembly.     

来源于中药和功能性食品的脂肪酸合酶抑制剂（英文）

肥胖症及其相关疾病已成为迫切需要解决的公共卫生问题。脂肪酸合酶（fatty acid synthase,FAS）是一种多功能复合酶,对长链脂肪酸的生物合成发挥至关重要的作用,是治疗肥胖、2型糖尿病、癌症、炎症和心血管疾病等的潜在靶点。在过去的30年里,FAS抑制剂的研究受到越来越多的关注。在中国,传统中药和功能性食品广泛被应用于慢性疾病的预防和治疗,其中有多种天然产物对FAS的活性表现出很强的抑制作用。本文综述了来源于中药和功能性食品中的FAS抑制剂结构和活性特点,为天然来源的FAS抑制剂治疗肥胖症和相关疾病提供了依据。     

Properties of a soluble thiosulfate sulfur transferase (rhodanese) of the marine methanogen Methanosarcina frisia

Abstract: Cell-free extracts of Methanosarcina frisia contain high thiosulfate sulfur transferase (TST) (rhodanese), slight thiosulfate reductase but no thiosulfate: acceptor oxidoreductase activity. Neither adenylylsulfate reductase nor sulfite: acceptor oxidoreductase activity could be detected. TST is an acidic protein with an M _r of 25 000 and was enriched by ion-exchange chromatography and gel filtration. The enzyme has a temperature optimum at 60°C and a pH optimum at pH 11. The K _m values for thiosulfate and cyanide are 0.53 mM and 1.57 mM, respectively. Low concentrations of cysteine, glutathione, dithioerythritol, and dihydrolipoate increase the activity of the enzyme while unphysiological concentrations of these effectors cause a decrease. Sulfite and N -bromosuccinimide inhibit the energy activity extremely.     

The thermodynamic landscape of testosterone binding to cytochrome P450 3A4: ligand binding and spin state equilibria

Human cytochrome P450 (CYP) 3A4 catalyzes the oxygen-dependent metabolism of greater than 60% of known drugs. CYP3A4 binds multiple ligands simultaneously, and this contributes to complex allosteric kinetic behavior. Substrates that bind to this enzyme change the ferric spin state equilibrium of the heme, which can be observed by optical absorbance and electron paramagnetic resonance (EPR) spectroscopy. The ligand-dependent spin state equilibrium has not been quantitatively understood for any ligands that exhibit multiple binding. The CYP3A4 substrate testosterone (TST) has been shown previously by absorbance spectroscopy to induce spin state changes that are characteristic of a low spin to high spin conversion. Here, EPR was used to examine the equilibrium binding of TST to CYP3A4 at [CYP3A4] > K(D), which allows for characterization of the singly occupied state (i.e., CYP3A4.TST). We also have used absorbance spectroscopy to examine equilibrium binding, where [CYP3A4] < K(D), which allows for determination of K(D)'s. The combination of absorbance and EPR spectroscopy at different CYP3A4 concentrations relative to K(D) and curve fitting of the resultant equilibrium binding titration curves to the Adair-Pauling equations, and modifications of it, reveals that the first equivalent of TST binds with higher affinity than the second equivalent of TST and its binding is positively cooperative with respect to ligand-dependent spin state conversion. Careful analysis of the EPR and absorbance spectral results suggests that the binding of the second TST induces a shift to the high spin state and thus that the second TST binding causes displacement of the bound water. A model involving six thermodynamic states is presented and this model is related to the turnover of the enzyme.     

铁硫蛋白的生物合成及相关疾病

铁硫蛋白是以铁硫簇为辅基,相对分子质量较小的一类蛋白质．它广泛存在于各种生物体内,参与电子传递、能量代谢以及基因表达调控等重要生理过程．其生物合成过程复杂,并且从细菌到人类高度保守．在真核细胞内,铁硫蛋白的组装由线粒体铁硫簇组装系统（mitochondrial iron sulfur cluster assembly system,mitochondrial ISC assembly system）和细胞质铁硫簇组装器（cytosolic iron sulfur cluster assembly,CIA）完成．研究发现,铁硫蛋白的合成异常可导致弗里德赖希共济失调(friedreich ataxia,FRDA)、遗传性肌病和铁粒幼细胞性贫血等多种罕见疾病,这些疾病严重影响个体的生活质量和寿命．因此,深入了解铁硫蛋白的结构和生物合成过程,对研究其生物学功能与相关疾病的诊断和治疗有重要意义．     

AMP-activated protein kinase is a key regulator of obesity-associated factors

An imbalance between caloric intake and energy expenditure leads to obesity. Obesity is an important risk factor for the development of several metabolic diseases including insulin resistance, metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. So, controlling obesity could be effective in the improvement of obesity-related diseases. Various factors are involved in obesity, such as AMP-activated protein kinases (AMPK), silent information regulators, inflammatory mediators, oxidative stress parameters, gastrointestinal hormones, adipokines, angiopoietin-like proteins, and microRNAs. These factors play an important role in obesity by controlling fat metabolism, energy homeostasis, food intake, and insulin sensitivity. AMPK is a heterotrimeric serine/threonine protein kinase known as a fuel-sensing enzyme. The central role of AMPK in obesity makes it an attractive molecule to target obesity and related metabolic diseases. In this review, the critical role of AMPK in obesity and the interplay between AMPK and obesity-associated factors were elaborated.     

Elucidation of the biosynthetic pathway for Okenone in Thiodictyon sp. CAD16 leads to the discovery of two novel carotene ketolases

Okenone is a unique ketocarotenoid found in many purple sulfur bacteria; it is important because of its unique light absorption and photoprotection properties. Okenane, a compound formed by diagenetic reduction of okenone, is an important biomarker in geochemical analyses of sedimentary rocks. Despite its ecological and biogeochemical importance, the biochemical pathway for okenone synthesis has not yet been fully described. The genome sequence of an okenone-producing organism, Thiodictyon sp. strain CAD16, revealed four genes whose predicted proteins had strong sequence similarity to enzymes known to produce ψ-end group modifications of carotenoids in proteobacteria. These four genes encoded homologs of a 1,2-carotenoid hydratase (CrtC), an O-methyltransferase (CrtF), and two paralogs of carotenoid 3,4-desaturases (CrtD). Expression studies in lycopene- or neurosporene-producing strains of Escherichia coli confirmed the functions of crtC and crtF, but the crtD paralogs encoded enzymes with previously undescribed functions. One enzyme, CruS, was only distantly related to CrtD desaturases, was bifunctional, and performed a 3,4-desaturation and introduced a C-2 keto group into neurosporene derivatives in the presence of dioxygen. The enzyme encoded by the other crtD paralog also represents a new enzyme in carotenogenesis and was named cruO. CruO encodes the C-4/4' ketolase uniquely required for okenone biosynthesis. The identification of CruO and the demonstration of its biochemical activity complete the elucidation of the biosynthetic pathway for okenone and other related ketocarotenoids.     

Evidence for thiosulfate sulfur transferase (rhodanese) trithionate reductase and tetrathionate reductase activities in Neisseria gonorrhoeae

Abstract Neisseria gonorrhoeae is unable to grow with sulfate but can use thiosulfate as sole source of sulfur.
Thiosulfate sulfur transferase (TST) (rhodanese) activity was present in the cytoplasmic soluble fraction. In the same extract, thiosulfate reductase (TSR), trithionate reductase and tetrathionate reductase activities were also detected using hydrogen as electron donor in the presence of viologen dyes and hydrogenase from Desulfovibrio gigas .
The significance of and the possible relationship between these different activities are discussed.     

GPR120的研究进展

游离脂肪酸作为组织能量来源以及介导各种细胞进程的信号分子,其生理功能长期以来受到广泛关注。外周游离脂肪酸水平的升高与肥胖、脂代谢紊乱以及糖尿病紧密相关。GPR120作为一新的长链脂肪酸受体,参与调节体内一系列的代谢过程,如激素分泌、细胞增殖及脂质生成等。作为肥胖、糖尿病的潜在治疗靶标,值得更深入的研究。     

Can the new adipokine asprosin be a metabolic troublemaker for cardiovascular diseases? A state-of-the-art review

Adipokines play a significant role in cardiometabolic diseases. Asprosin, a newly discovered adipokine, was first identified as a glucose-raising protein hormone. Asprosin also stimulates appetite and regulates glucose and lipid metabolism. Its identified receptors so far include Olfr734 and Ptprd. Clinical studies have found that asprosin may be associated with cardiometabolic diseases. Asprosin may have diagnostic and therapeutic potential in obesity, diabetes, metabolic syndrome and atherosclerotic cardiovascular diseases. Herein, the structure, receptors, and functions of asprosin and its relationship with cardiometabolic diseases are summarized based on recent findings.     

Testosterone sulfotransferase: evidence in the guinea pig that this reaction is carried out by 3 alpha-hydroxysteroid sulfotransferase.

During the course of isolating, characterizing, and cloning estrogen and 3-hydroxysteroid sulfotransferases from the guinea pig adrenal gland, it was noted that cytosolic preparations from this tissue would also sulfonate testosterone. Therefore, we set out to isolate and clone the enzyme that performs this reaction. Testosterone sulfotransferase (TST) was isolated from the guinea pig adrenal by using the standard procedures of ion exchange, affinity, and high-performance liquid chromatography. When purified, TST was examined by liquid-phase nondenaturing isoelectric focusing, it was found that the TST activity profile completely overlapped with the activity profile of the 3alpha-hydroxysteroid sulfotransferase (3alphaHST) isoform, but not the 3beta-hydroxysteroid sulfotransferase (3betaHST) isoform. This finding was further investigated by overexpressing the cDNAs for 3alphaHST and 3betaHST in Escherichia coli and examining the expressed proteins for TST activity. This experiment confirmed that 3alphaHST does indeed function as a TST. In addition, 3alphaHST was also found to sulfonate estradiol but not estrone, a finding that further suggested that 3alphaHST may function as a general 17beta-hydroxysteroid sulfotransferase.     

The emerging roles of ubiquitin-like protein Urm1 in eukaryotes

The ubiquitin related modifier Urm1 protein was firstly identified in the yeast Saccharomyces cerevisiae, and was later found to play important roles in different eukaryotes. By the assistance of an E1-like activation enzyme Uba4, Urm1 can function as a modifier to target proteins, called urmylation. The thioredoxin peroxidase Ahp1 was the only identified Urm1 target in the early time. Recently, many other Urm1 targets were identified, which is important for us to fully understand functions of urmylation. Urm1 can also function as a sulfur carrier to play a key role in tRNAs thiolation. Mechanisms of the Urm1 in protein and RNA modifications were finely revealed in the past few years. Biological and physiological functions of Urm1 were also found in different organisms. In this review, we will summarize these emerging progresses.     

Galanin and its receptors: a novel strategy for appetite control and obesity therapy

The rapid increase in the prevalence of overweight and obesity is becoming an important health problem. Overweight and obesity may cause several metabolic complications, including type 2 diabetes mellitus, hyperlipidemia, high cholesterol, coronary artery disease as well as hypertension. Prevention and treatment of obesity will benefit the treatment of these related diseases. Current strategies for treatment of obesity are not adequately effective and are frequently companied with many side effects. Thus, new ways to treat obesity are urgently needed. Galanin is undoubtedly involved in the regulation of food intake and body weight. The aim of this review is to provide up-to-date knowledge concerning the roles of central and peripheral galanin as well as its receptors in the regulation of metabolism, obesity and appetite. We also highlight the mechanisms of galanin and its receptors in experimental obesity, trying to establish a novel anti-obesity strategy.     

Body fatness and its social and lifestyle determinants in young working males from Cracow, Poland

The aim of this study was to determine the degree to which general body fatness variation, presented by body mass index (BMI), the sum of the three skinfold thicknesses (TST) (triceps, subscapular, abdominal) and percentage of body fat (%FAT), can be explained by socioeconomic status (SES) and lifestyle. The cross-sectional, population-based survey was of 259 healthy working males aged 20-30 from the city of Cracow, Poland. Objective anthropometric measurements, bioelectrical impedance analysis, the results of motor fitness tests and social and lifestyle data from a questionnaire were analysed. The independent variables were: age, socioeconomic status (birthplace, place of residence until the age of 14, social class, educational level and the type of work done) and lifestyle elements (smoking habits, dietary habits, family obesity resemblance, sport activity in the past, leisure time physical activity and level of motor fitness). Three separate full models were created using stepwise straightforward regression with BMI, TST and %FAT as dependent variables. The highest autonomous influence on BMI and %FAT was ascribed to age and family obesity resemblance, whereas variation in TST was explained by level of motor fitness, age, city as a place of residence until the age of 14 and family obesity resemblance. Although the analysed variables explained only from 8% (BMI) to 13% (TST) of body fatness variation, indicating at the same time that most variations are explained by other variables, the impact of lifestyle family-shared factors on body fatness seems to be significant.     

PGC-1α的功能与代谢病

过氧化物酶体增殖活化受体γ辅助活化因子1α(α subunit of peroxisome proliferators activated receptor γ coactivator 1,PGC-1α)是过氧化物酶体增殖活化受体γ辅助活化因子1 (PGC 1)的成员之一. PGC-1α是与能量代谢 关系密切的1个转录辅助活化因子,在线粒体合成、调节适应性产热、骨骼肌纤维类型转换等过程中发挥重要作用.同时,还 参与到糖代谢、脂代谢中,已成为治疗糖尿病、肥胖等代谢疾病的新靶点.近年来还发现, PGC-1α对治疗癌症发生及神经 变性疾病有一定作用.本文主要从PGC-1α调节适应性产热、促进线粒体合成、在骨骼肌中调节纤维类型转换及葡萄糖代谢 等方面对其生理功能进行阐述,并对 PGC-1α与相关代谢疾病的关系进行了总结.     

Dose and Time‐Dependent Effects of Cyanide on Thiosulfate Sulfurtransferase, 3‐Mercaptopyruvate Sulfurtransferase,and Cystathionine λ‐Lyase Activities

We assessed the dose‐dependent effect of potassium cyanide (KCN) on thiosulfate sulfurtransferase (TST), 3‐mercaptopyruvate sulfurtransferase (3‐MPST), and cystathionine λ‐lyase (CST) activities in mice. The time‐dependent effect of 0.5 LD50 KCN on cyanide level and cytochrome c oxidase (CCO), TST, 3‐MPST, and CST activities was also examined. Furthermore, TST, 3‐MPST, and CST activities were measured in stored mice cadavers. Hepatic and renal TST activity increased by 0.5 LD50 KCN but diminished by ≥2.0 LD50. After 0.5 LD50 KCN, the elevated hepatic cyanide level was accompanied by increased TST, 3‐MPST, and CST activities, and CCO inhibition. Elevated renal cyanide level was only accompanied by increased 3‐MPST activity. No appreciable change in enzyme activities was observed in mice cadavers. The study concludes that high doses of cyanide exert saturating effects on its detoxification enzymes, indicating their exogenous use during cyanide poisoning. Also, these enzymes are not reliable markers of cyanide poisoning in autopsied samples.     

PPARα,γ和δ:胰岛素抵抗治疗的靶点

胰岛素抵抗(insulin resistance,IR)是指外周组织对胰岛素的反应敏感性降低,是肝脏疾病和心血管病发生的共同基础,常常是高脂血症和2型糖尿病发病的前奏.过氧化物酶体增殖物激活受体(peroxisome proliferator-activated receptors,PPARs)属于核受体超家族的成员.PPARs激动剂可通过多种途径改善胰岛素敏感性,例如调节糖脂代谢、抗炎作用以及间接地改善氧化应激状态.这篇综述主要是回顾IR的病理机制及其治疗靶点:PPARα,δ和γ,并阐明针对此类靶点的胰岛素增敏药物的信号转导通路.     

Apelin/APJ 系统对能量代谢及其相关疾病调控的影响

G蛋白偶联受体APJ及其内源性配体Apelin在许多外周组织和中枢神经系统中高度表达,包括骨骼肌、胰腺、脂肪组织和下丘脑。Apelin /APJ系统调控许多生理功能,如调节血管生成,液体体内平衡和能量代谢;同时还参与不同疾病的发生发展,如糖尿病及其并发症、肥胖等。越来越多的证据表明,Apelin/APJ系统能调节胰岛素敏感性,刺激葡萄糖利用缓解糖尿病的形成;Apelin/APJ系统还能缓解肥胖引起的高血压、心血管等疾病;同时Apelin/APJ系统能促进肿瘤细胞的增殖与迁移。这篇综述旨在介绍Apelin /APJ系统在人体内各组织中可能存在的能量代谢调节功能及其对相关代谢性疾病的调控,Apelin /APJ系统有望成为潜在的用于治疗代谢性疾病的分子靶标。     

基于肠道微生态探讨黄连素在代谢性疾病中的抗炎作用

肠道菌群与能量代谢密切相关,其组成和代谢紊乱可通过多种途径导致胰岛素抵抗,肥胖和2型糖尿病。黄连素因具有减重、降糖、调脂等作用被广泛用于肥胖、2型糖尿病及非酒精性脂肪性肝病等代谢性疾病的辅助治疗;研究表明,黄连素可调节肠道菌群的组成和代谢,改善肠道微生态环境,从而改善胰岛素抵抗和代谢。本文综述了黄连素通过肠道菌群-炎症轴在干预代谢性疾病的研究进展,以期为代谢性疾病的治疗寻找新的策略,并为今后该领域的深入研究提供指导意义。     

A novel thermodynamic relationship based on Kramers Theory for studying enzyme kinetics under high viscosity

In most studies of enzyme kinetics it has been found sufficient to use the classical Transition State Theory (TST) of Eyring and others. This theory was based on the solvent being an ideal dilute substance treated as a heat bath. However, enzymes found in organisms adapted to very low (psychrophiles) and very high (thermophiles) temperatures are also subjected to variable solute concentrations and viscosities. Therefore, the TST may not always be applicable to enzyme reactions carried out in various solvents with viscosities ranging from moderate to very high. There have been numerous advances in the theory of chemical reactions in realistic non-ideal solvents such as Kramers Theory. In this paper we wish to propose a modified thermodynamic equation, which have contributions from kcat, Km and the viscosity of the medium in which the enzyme reaction is occurring. These could be very useful for determining the thermodynamics of enzymes catalyzing reactions at temperature extremes in the presence of substrate solutions of different compositions and viscosities.