蔬菜硝酸盐含量与硝酸还原酶活性的研究

对镇江地区9种主要蔬菜70个样品的硝酸盐含量测定结果表明, 该地区根、茎、叶类蔬菜硝酸盐污染较严重,其中以小青菜、茼蒿、芹菜、萝卜、蕹菜和苋菜最为突出,莴苣其次,生菜和土豆较轻。50mmol/L硝酸钾诱导下,各种蔬菜幼苗组织的硝酸还原酶活性(NRA)增加,但变化规律不同。不同浓度的硝酸钾诱导2h,蔬菜叶片中NRA也增加,但峰值浓度不同。NRA高的蔬菜对硝酸盐的耐受性好,诱导后高活性作用时间长。     

In Vitro and In Silico Analysis of New n-Butyl and Isobutyl Quinoxaline-7-carboxylate 1,4-di-N-oxide Derivatives against Trypanosoma cruzi as Trypanothione Reductase Inhibitors

American trypanosomiasis is a worldwide health problem that requires attention due to ineffective treatment options. We evaluated n-butyl and isobutyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives against trypomastigotes of the Trypanosoma cruzi strains NINOA and INC-5. An in silico analysis of the interactions of 1,4-di-N-oxide on the active site of trypanothione reductase (TR) and an enzyme inhibition study was carried out. The n-butyl series compound identified as T-150 had the best trypanocidal activity against T. cruzi trypomastigotes, with a 13% TR inhibition at 44 μM. The derivative T-147 behaved as a mixed inhibitor with Ki and Ki’ inhibition constants of 11.4 and 60.8 µM, respectively. This finding is comparable to the TR inhibitor mepacrine (Ki = 19 µM).     

Relevance of Plasma Homocysteine and Methylenetetrahydrofolate Reductase 677TT Genotype in Sickle Cell Disease: A Systematic Review and Meta-Analysis

We evaluated the relevance of plasma homocysteine (HC) and the TT genotype of the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism (rs1801133) in sickle cell disease (SCD) and associated vaso-occlusive crisis (VOC) and ischemic stroke (IS). We identified in Embase and Medline 22 studies on plasma HC and 22 on MTHFR genotypes. Due to age-related HC differences, adult and paediatric SCD were separated: 879 adult SCD and 834 controls (CTR) yielded a neutral effect size; 427 paediatric SCD and 625 CTR favoured SCD (p = 0.001) with wide heterogeneity (I² = 95.5%) and were sub-grouped by country: six studies (Dutch Antilles n = 1, USA n = 5) yielded a neutral effect size, four (India n = 1, Arab countries n = 3) favoured SCD (p < 0.0001). Moreover, 249 SCD in VOC and 419 out of VOC yielded a neutral effect size. The pooled prevalence of the MTHFR TT genotype in 267 SCD equalled that of 1199 CTR (4.26% vs. 2.86%, p = 0.45), and in 84 SCD with IS equalled that of 86 without IS (5.9% vs. 3.7%, p = 0.47); removal of one paediatric study yielded a significant effect size (p = 0.006). Plasma HC in paediatric SCD from Middle East and India was higher, possibly due to vitamin deficiencies. Despite its low prevalence in SCD, the MTHFR TT genotype relates to adult IS.     

亚硝酸盐还原酶对咸鱼中亚硝酸盐的降解条件与效果研究

为了探明亚硝酸盐还原酶（Nitrite Reductase,NiRs）对咸鱼中亚硝酸盐的降解作用及应用条件,实验以亚硝酸盐降解量为评价指标,通过单因素实验和Design-expert响应面实验分析咸鱼加工过程中加入亚硝酸盐还原酶（NiRs）的酶浓度、温度、时间的最适条件,并通过测定色差值和感官指标分析NiRs对咸鱼品质的影响。结果表明:NiRs在咸鱼加工中的最佳应用条件是酶浓度4mg/m L、温度34℃、时间5h,亚硝酸盐降解率可达到32.7%。加入NiRs不影响咸鱼的品质,对咸鱼风味有提升作用。研究结果表明在咸鱼生产中添加NiRs可有效降解亚硝酸盐,在保证咸鱼的食用安全性的同时,为腌制水产品的加工提供理论依据和技术支撑。      

Light-Dependent Nitrate Removal Capacity of Green Microalgae

In the present study, Chlamydomonas sp. MACC-216 was used to investigate total nitrate removal in TAP medium with sodium nitrate as the sole nitrogen source under several light conditions made up of permuted combinations of three light colors (referred to as blue, red, and white light) and three light intensities (50 µmol m⁻² s⁻¹, 100 µmol m⁻² s⁻¹, and 250 µmol m⁻² s⁻¹). It was observed that nitrate removal efficiency is influenced by light color as well as light intensity. Additionally, Chlamydomonas sp. MACC-216 was cultivated in synthetic wastewater under four light conditions, namely, Blue 250, Blue 125 + Red 125, Red 250, and White 250, where it showed the highest nitrate removal efficiency and nitrate reductase activity under the Blue 125 + Red 125 light condition. To observe the impact of light color on the nitrate removal capacity of Chlamydomonas sp. MACC-216, the expression of five genes participating in nitrate transport and reduction (NRT1, NRT2.1, NRT2.2, NIA, and MCP) was also analyzed; these genes showed the highest expression under the Blue 125 + Red 125 light condition. Based on the above-mentioned findings, the blue + red light combination emerged as a promising light combination for nitrate removal. Hence, our study suggests the importance of the blue + red light combination together with high light intensity, as the optimal light condition for nitrate removal from synthetic wastewater in comparison to other monochromatic lights with high light intensity.     

The Magnetosome Protein,Mms6 from Magnetospirillum magneticum Strain AMB-1, Is a Lipid-Activated Ferric Reductase

Magnetosomes of magnetotactic bacteria consist of magnetic nanocrystals with defined morphologies enclosed in vesicles originated from cytoplasmic membrane invaginations. Although many proteins are involved in creating magnetosomes, a single magnetosome protein, Mms6 from Magnetospirillum magneticum strain AMB-1, can direct the crystallization of magnetite nanoparticles in vitro. The in vivo role of Mms6 in magnetosome formation is debated, and the observation that Mms6 binds Fe³⁺ more tightly than Fe²⁺ raises the question of how, in a magnetosome environment dominated by Fe³⁺, Mms6 promotes the crystallization of magnetite, which contains both Fe³⁺ and Fe²⁺. Here we show that Mms6 is a ferric reductase that reduces Fe³⁺ to Fe²⁺ using NADH and FAD as electron donor and cofactor, respectively. Reductase activity is elevated when Mms6 is integrated into either liposomes or bicelles. Analysis of Mms6 mutants suggests that the C-terminal domain binds iron and the N-terminal domain contains the catalytic site. Although Mms6 forms multimers that involve C-terminal and N-terminal domain interactions, a fusion protein with ubiquitin remains a monomer and displays reductase activity, which suggests that the catalytic site is fully in the monomer. However, the quaternary structure of Mms6 appears to alter the iron binding characteristics of the C-terminal domain. These results are consistent with a hypothesis that Mms6, a membrane protein, promotes the formation of magnetite in vivo by a mechanism that involves reducing iron.     

密闭气体环境对夏菠菜硝酸盐、亚硝酸盐及贮藏品质的影响

以菠菜为实验材料,研究低温贮藏条件下(4℃)密闭气体环境对菠菜贮藏品质,尤其对硝酸盐、亚硝酸盐及硝酸还原酶等酶活性的影响。结果表明:与对照(非密闭环境)相比,低温密闭气体环境可显著减缓菠菜可溶性固形物、VC、叶绿素等贮藏品质的下降,维持菠菜较高的硝酸还原酶(NR)活性和抗逆酶活性(SOD、POD、CAT),抑制丙二醛的产生,贮藏8d硝酸盐和亚硝酸盐分别为1318.44、0.42mg/kg,较对照分别降低了31.96%、26.19%,实验表明低温密闭气体环境有效降低了硝酸盐和亚硝酸盐的累积,提升了菠菜的安全贮运品质。      

产亚硝酸还原酶基因工程菌pET-28a(+)-nir-BL21的培养基优化

从豆瓣酱中筛选的一株能高效降解亚硝酸盐的蜡样芽孢杆菌(Bacillus cereus)LJ01,将其nir基因克隆至相应的表达载体上,构建了重组菌pET-28a(+)-nir-BL21。为提高基因工程菌pET-28a(+)-nir-BL21的产亚硝酸盐还原酶(NiR)水平,对重组菌pET-28a(+)-nir-BL21的培养基组成通过单因素实验、Plackett-Burman和Box-Behnken试验优化。结果表明,获得最佳培养基为:以液体LB培养基为基础培养基,再添加葡萄糖3.72 g·L^-1、甘油2.63 g·L^-1和细菌学蛋白胨8.70 g·L^-1,活菌数预测值为3.14×10⁸ CFU·mL^-1,通过验证得3.02×10⁸ CFU·mL^-1,与预测值接近。本实验构建的高产亚硝酸盐还原酶的菌株,将为日后降解食品中的亚硝酸盐进行工业化应用提供理论基础。     

Identification of potential inhibitors for Sterol C-24 reductase of <i>Leishmania donovani</i> through virtual screening of natural compounds

Leishmaniasis is a vector-borne parasitic neglected tropical disease caused by a group of about 30 different species of the genus Leishmania. It is transmitted by the bite of female phlebotomies sand fly. Three main clinical manifestations of leishmaniasis include cutaneous, visceral, and mucocutaneous leishmaniasis. Visceral leishmaniasis (VL) caused by Leishmania donovani, is an infection of reticuloendothelial system and fatal if untreated. Cholesterol, a sterol that is prominent in the mammalian cell membranes whereas stigmasterol and ergosterol are more prevalent in plants, yeast, and protozoa, respectively. Ergosterols which is absent in human being, is an important constituent of parasite membrane. Sterol C-24 reductase (LdSR) enzyme catalyzes the final step in the ergosterol biosynthesis pathway. The inhibition of biosynthesis of ergosterol may lead to decreased cell viability and growth. Here, we performed the molecular docking-based virtual screening of a library of natural ligands against LdSR to identify a potential inhibitor to fight leishmaniasis. Capsaicin, prenyletin, flavan-3-ol, resveratrol, and gingerol showed the top binding affinity towards LdSR. Based upon ADME properties and bioactivity score, gingerol showed the best lead-likeness and drug-likeness properties. Hence, we further annotated its leishmanicidal properties. We found that gingerol inhibited the growth and proliferation of promastigotes as well as intra-macrophagic amastigotes. Gingerol exerted its antileishmanial action through the induction of reactive oxygen species (ROS) in concentration-dependent manner. Gingerol induced ROS led to apoptosis. Overall, this study described that gingerol would act as possible inhibitor to LdSR.