Biosynthesis of Monoterpenoid Indole AlkaloidAjmaline Catalyzed by Novel Reductases

Introduction One of the major root alkaloids of the Indian medicinal plant Rauvolfia serpenlina Benth. ex Kurz is named ajmaline. The enzymatic biosynthesis of this alkaloid has been studied for a long time by our group As a result, a biosynthetic pathway has been established, in which about 10 enzymes participate, several of them belonging to the group of NADPH-dependent reductases. Started with the biosynthetic precursors tryptamine and secologanin,

Thioredoxin and glutaredoxin-mediated redox regulation of ribonucleotide reductase

Ribonucleotide reductase(RNR), the rate-limitingenzyme in DNA synthesis, catalyzes reduction of thedifferent ribonucleotides to their corresponding deoxyri-bonucleotides. The crucial role of RNR in DNA synthesishas made it an important target for the development ofantiviral and anticancer drugs. Taking account of the re-cent developments in this field of research, this reviewfocuses on the role of thioredoxin and glutaredoxin sys-tems in the redox reactions of the RNR catalysis.

Emerging roles of the ribonucleotide reductase M2 in colorectal cancer and ultraviolet-induced DNA damage repair

AIM:To investigate the roles of the ribonucleotide reductase M2 (RRM2) subunit in colorectal cancer (CRC) and ultraviolet (UV)-induced DNA damage repair. METHODS:Immunohistochemical staining of tissue microarray was performed to detect the expression of RRM2. Seven CRC cell lines were cultured and three human colon cancer cell lines, i.e., HCT116, SW480 and SW620, were used. Reverse transcription polymerase chain reaction and Western blotting were performed to determine the mRNA and protein expression levels of RRM2, respectively. Cell proliferation assay, cell cycle analysis were performed. Cell apoptosis was evaluated by double staining with fluorescein isothiocyanate-conjugated Annexin Ⅴ and propidium iodide (PI) usingAnnexin Ⅴ/PI apoptosis kit. The motility and invasion of CRC cells were assessed by the Transwell chamber assay. Cells were irradiated with a 254 nm UV-C lamp to detect the UV sensitivity after RRM2 depletion. RESULTS:Immunohistochemical staining revealed elevated RRM2 levels in CRC tissues. RRM2 overexpression was positively correlated with invasion depth (P < 0.05), poorly differentiated type (P = 0.0051), and tumor node metastasis stage (P = 0.0015). The expression of RRM2 in HCT116 cells was downregulated after transfection, and HCT116 cell proliferation was obviously suppressed compared to control groups (P < 0.05). In the invasion test, the number of cells that passed through the chambers in the RRM2-siRNA group was 81 ± 3, which was lower than that in the negative control (289 ± 7) and blank control groups (301 ± 7.2). These differences were statistically significant (P < 0.01). Our data suggest that RRM2 overexpression may be associated with CRC progression. RRM2 silencing by siRNA may inhibit the hyperplasia and invasiveness of CRC cells, suggesting that RRM2 may play an important role in the infiltration and metastasis of CRC, which is a potential therapeutic strategy in CRC. In addition, RRM2 depletion increased UV sensitivity. CONCLUSION:These findings suggest that RRM2 may be a facilitating factor in colorectal tumorigenesis and UV-induced DNA damage repair.

Expression of <i>T4HR1</i>, a 1,3,6,8-Tetrahydroxynaphthalene Reductase Gene Involved in Melanin Biosynthesis, Is Enhanced by Near-Ultraviolet Irradiation in <i>Bipolaris oryzae</i>

Bipolaris oryzae is the causal agent of brown spot disease in rice and produces the dark pigment melanin. We isolated and characterized T4HR1 gene encoding 1,3,6,8-tetrahydroxynaphthalene (1,3,6,8-THN) reductase, which converted 1,3,6,8-THN to scytalone in the melanin biosynthesis from B. oryzae. A sequence analysis showed that the T4HR1 gene encoded a putative protein of 268 amino acids showing 50% - 99% sequence identity to other fungal 1,3,6,8-THN reductases. Targeted disruption of the T4HR1 gene showed a different phenotype of mycelial color due to an accumulation of shunt products compared to those of wild-type on PDA plates using tricyclazole as a melanin biosynthesis inhibitor. A quantitative real-time PCR analysis showed that the expression of T4HR1 transcripts was enhanced by near-ultraviolet (NUV) irradiation and regulated by transcriptional factor BMR1, similar to three other melanin biosynthesis genes (polyketide synthase gene [PKS1], scytalone dehydratase gene [SCD1], and 1,3,8-THN reductase gene [THR1]) in the melanin biosynthesis of B. oryzae. These results suggested that common transcriptional mechanisms could regulate the enhanced gene expression of these melanin biosynthesis genes by NUV irradiation in B. oryzae.

Screening of traditional Chinese medicine monomers as ribonucleotide reductase M2 inhibitors for tumor treatment

BACKGROUND Ribonucleotide reductase(RR)is a key enzyme in tumor proliferation,especially its subunit-RRM2.Although there are multiple therapeutics for tumors,they all have certain limitations.Given their advantages,traditional Chinese medicine(TCM)monomers have become an important source of anti-tumor drugs.Therefore,screening and analysis of TCM monomers with RRM2 inhibition can provide a reference for further anti-tumor drug development.AIM To screen and analyze potential anti-tumor TCM monomers with a good binding capacity to RRM2.METHODS The Gene Expression Profiling Interactive Analysis database was used to analyze the level of RRM2 gene expression in normal and tumor tissues as well as RRM2's effect on the overall survival rate of tumor patients.TCM monomers that potentially act on RRM2 were screened via literature mining.Using AutoDock software,the screened monomers were docked with the RRM2 protein.RESULTS The expression of RRM2 mRNA in multiple tumor tissues was significantly higher than that in normal tissues,and it was negatively correlated with the overall survival rate of patients with the majority of tumor types.Through literature mining,we discovered that berberine,ursolic acid,gambogic acid,cinobufagin,quercetin,daphnetin,and osalmide have inhibitory effects on RRM2.The results of molecular docking identified that the above TCM monomers have a strong binding capacity with RRM2 protein,which mainly interacted through hydrogen bonds and hydrophobic force.The main binding sites were Arg330,Tyr323,Ser263,and Met350.CONCLUSION RRM2 is an important tumor therapeutic target.The TCM monomers screened have a good binding capacity with the RRM2 protein.

Electron Donor Systems to Facilitate Development of Assays for Two Flavoproteins Involved in Tetrahydromethanopterin Biosynthesis

Methane production by archaea depends on tetrahydromethanopterin (H4MPT), a pterin-containing cofactor that carries one-carbon units. Two redox reactions within the nine steps of H4MPT side chain biosynthesis have been hypothesized. Biochemical assays have demonstrated that the archaeal iron-sulfur flavoprotein dihydromethanopterin reductase X (DmrX or MM1854) catalyzes the final reaction of the pathway, the reduction of dihydromethanopterin to H4MPT, using dithiothreitol (DTT) as an artificial electron donor. The crystal structure of DmrB, a bacterial DmrX homolog that lacks iron-sulfur clusters, has led to a proposed ping-pong mechanism of electron transfer between FMNH2 and the FMN prosthetic group of DmrB. However, an enzymatic assay to test the hypothetical DmrB mechanism is lacking because a suitable electron donor has not previously been identified. Furthermore, a second uncharacterized archaeal flavoprotein (MM1853) has been hypothesized to function in H4MPT side chain biosynthesis. In this work, to facilitate the development of assays to elucidate the functions of DmrB and MM1853, we tested a variety of electron donors, including dithiothreitol, ferredoxin, and a system consisting of NADH and an NADH-dependent flavin-reducing enzyme (Fre). Reduction of the DmrB prosthetic group (FMN) was measured as a decrease in absorbance at 460 nm. NADPH, NADH, and DTT were unable to reduce DmrB. However, NADH/Fre was able to reduce DmrB within 70 min (initial rate of 1.3 μM/min), providing the basis for a future DmrB activity assay. Carbon monoxide (CO)/CO dehydrogenase/ferredoxin reduced DmrB more rapidly within 6 min. Both electron transfer systems reduced a second flavin-containing archaeal protein MM1853, which is predicted to catalyze the third step of H4MPT biosynthesis. While NADH and NADPH were incapable of directly reducing the FMN cofactor of MM1853, DTT or NADH/Fre could eliminate the FMN peaks. These results establish the basis for new oxidoreductase assays that will facilitate testing several proposed DmrB mechanisms and defining the specific function of MM1853 in methanogen cofactor biosynthesis.

Overexpression of ribonucleotide reductase small subunit,RNRM,increases cordycepin biosynthesis in transformed Cordyceps militaris

Cordycepin was the first adenosine analogue used as an anticancer and antiviral agent, which is extracted from Cordyceps militaris and hasn’t been biosynthesized until now. This study was first conducted to verify the role of ribonucleotide reductases(RNRs, the two RNR subunits, RNRL and RNRM) in the biosynthesis of cordycepin by over expressing RNRs genes in transformed C. militaris. Quantitative real-time PCR(qRT-PCR) and western blotting results showed that the m RNA and protein levels of RNR subunit genes were significantly upregulated in transformant C. militaris strains compared to the control strain. The results of the HPLC assay indicated that the cordycepin was significantly higher in the C. militaris transformants carrying RNRM than in the wildtype strain, whereas the RNRML was preferentially downregulated. For the C. militaris transformant carrying RNRL, the content of cordycepin wasn’t remarkably changed. Furthermore, we revealed that inhibiting RNRs with Triapine(3-AP) almost abrogated the upregulation of cordycepin. Therefore, our results suggested that RNRM can probably directly participate in cordycepin biosynthesis by hydrolyzing adenosine, which is useful for improving cordycepin synthesis and helps to satisfy the commercial demand of cordycepin in the field of medicine.

吸烟对非小细胞肺癌患者ERCC1和RRM1表达的影响及与预后的相关性

目的探讨吸烟对非小细胞肺癌(NSCLC)患者切除修复交叉互补基因1(ERCC1)和核糖核苷酸还原酶M1(RRM1)表达的影响及其与预后的关系。方法收集2015年8月至2018年8月河南科技大学第一附属医院收治的131例ⅢB期、Ⅳ期的NSCLC患者。依据有无吸烟史将患者分为两组,其中非吸烟组64例,吸烟组67例,检测各组ERCC1和RRM1的表达水平,分析其与患者临床资料的相关性以及对患者预后的影响。结果吸烟组ERCC1高表达患者占比多于非吸烟组(P<0.05);两组ERCC1和RRM1的表达水平与患者性别、年龄、肿瘤大小、病理类型无关(P>0.05);吸烟指数≥400的患者ERCC1表达较高(P=0.018);两组ERCC1和RRM1低表达的患者化疗有效率均高于高表达患者(χ^(2)=6.194,P=0.013;χ^(2)=5.012,P=0.025);与吸烟组比较,非吸烟组化疗有效率高(P=0.045),1 a复发率低(P=0.001),无进展生存期(P=0.008)和总生存期长(P=0.005)。结论吸烟影响ERCC1的表达,且吸烟指数越高的患者ERCC1表达越高;而RRM1的表达与吸烟无关。吸烟患者化疗有效率、1 a复发率低于非吸烟患者,无进展生存期及生存期均短于非吸烟患者。

Dihydrofolate reductase-like protein inactivates hemiaminal pharmacophore for self-resistance in safracin biosynthesis

Dihydrofolate reductase(DHFR),a housekeeping enzyme in primary metabolism,has been extensively studied as a model of acid-base catalysis and a clinic drug target.Herein,we investigated the enzymology of a DHFR-like protein SacH in safracin(SAC)biosynthesis,which reductively inactivates hemiaminal pharmacophore-containing biosynthetic intermediates and antibiotics for self-resistance.Furthermore,based on the crystal structure of SacH−NADPH−SAC-A ternary complexes and mutagenesis,we proposed a catalytic mechanism that is distinct from the previously characterized short-chain dehydrogenases/reductases-mediated inactivation of hemiaminal pharmacophore.These findings expand the functions of DHFR family proteins,reveal that the common reaction can be catalyzed by distinct family of enzymes,and imply the possibility for the discovery of novel antibiotics with hemiaminal pharmacophore.

Ribonucleotide reductase metallocofactor： assembly, maintenance and inhibition

Ribonucleotide rcductase （RNR） supplies cellular deoxyribonucleotidc triphosphates （dNTP） pools by converting ribonucleotides to the corresponding deoxy forms using radical-based chemistry. Eukaryotic RNR comprises a and β subunits： u contains the catalytic and ailosteric sites; β houses a diferric-tyrosyl radical cofactor （FeⅢ2-Y· ） that is required to initiates nucleotide reduction in α. Cells have evolved multi-layered mechanisms to regulate RNR level and activity in order to maintain the adequate sizes and ratios of their dNTP pools to ensure high- fidelity DNA replication and repair. The central role of RNR in nucleotide metabolism also makes it a proven target of chemotherapeutics. In this review, we discuss recent progress in understanding the function and regulation of eukaryofic RNRs, with a focus on studies revealing the cellular machineries involved in RNR metaUocofactor biosynthesis and its implication in RNR-targeting therapeutics.

UDP-糖生物合成的研究进展

尿苷二磷酸(UDP)-糖是糖基化修饰利用的一类重要糖供体,从合酶途径、磷酸化酶途径和激酶途径总结UDP-糖的体内合成过程,由于关键酶的缺乏,只有UDP-葡萄糖(UDP-Glc)能从以上3种途径快速合成。通过特定功能酶能够实现UDP-糖之间快速转化,这种转化以UDP-葡萄糖为起始物,以UDP-葡萄糖醛酸(UDP-GlcA)为中间体,在此基础上,概述特定功能酶催化UDP-糖合成的最新进展,探讨脱氢酶、脱羧酶、异构酶和还原酶在UDP-糖转化中的重要作用。最后,剖析UDP-糖合成的现存问题,展望UDP-糖合成的未来研究方向,旨在为更快地挖掘UDP-糖基供体的作用潜能和实现更加高效低成本的糖基化修饰提供新思路。

膀胱癌组织中脂肪酸结合蛋白6、核苷酸还原酶M1亚基的表达及与临床病理特征的相关性

目的:探究膀胱癌(bladder cancer)组织中脂肪酸结合蛋白6(fatty acid-binding protein6,FABP6)、核苷酸还原酶M1亚基(ribonucleotide reductase regulatory subunit M1,RRM1)的表达水平及其与膀胱癌患者临床病理特征的相关性。方法:回顾性分析2020年2月-2021年12月大冶市人民医院收治的并接受手术切除的40例膀胱癌患者的临床资料。采用免疫组化法检测各组织中的FABP6和RRM1蛋白表达水平,并分析FABP6和RRM1蛋白与各项临床特征的关系。结果:膀胱癌组织中FABP6和RRM1高蛋白表达水平占比均高于癌旁正常组织(P<0.05)。FABP6和RRM1蛋白高表达和低表达膀胱癌患者的性别、年龄、肿瘤类型、肿瘤直径比较,差异均无统计学意义(P>0.05)。FABP6和RRM1蛋白高表达和低表达膀胱癌患者的分化程度、TNM分期、淋巴结转移比较,差异均有统计学意义(P<0.05)。结论:FABP6、RRM1在膀胱癌组织中表达水平高于癌旁正常组织,且两者均参与了膀胱癌的发生、发展进程。

18F-fluorodeoxyglucose Uptake with Expression of Excision Repair Cross-complementary Group I and Ribonucleotide Reductase Subunit M1 in Non-small Cell Lung Cancer

Fluorodeoxyglucose positron emission tomography/conlputed tomography （FDG PET/CT） is widely applied in non-small cell lung cancer （NSCLC）. The standardized uptake value （SUV）, a semi-quantitative index, plays an essential role in NSCLC tbr diagnosis, staging, and efficacy evaklation. It has been px3posed that the SUV of tumors may correlate with the presence or absence of chemotherapy resistance-associated biomarkers based on studies that have displayed a close correlation between SUV and the expression levels of excision repair cross-complementary Group 1 （ERCC 1 ）1~1 and Tp53-induced glycolysis and apoptosis regulator.121 FDG avidity of NSCLC and ERCC 1 and ribonucleotide reductase subunit M 1 （RRM 1 ） levels have not been as extensively investigated. Based on these findings, we looked tbr correlations among metabolic parameters （SUVm,,. metabolic tumor volume [MTV], and total lesion glycolysis [TLG]） and ERCC1 and RRM1 expression in patients with NSCLC, to investigate whether FDG uptake reflects the presence or absence ofchemoresistance proteins （ERCC1 and RRM 1 ） within tumor cells.

核糖核苷酸还原酶研究

核糖核苷酸还原酶广泛存在于各种生物中,是生物体内唯一的催化4种核糖核苷酸还原、生成相应的脱氧核糖核苷酸的酶。该酶是DNA合成和修复的关键酶和限速酶,对细胞的增殖和分化起着调控作用。不同生物中的RR根据其结合的金属辅助因子不同而分类。虽然不同类型RR之间的氨基酸序列相似性很低,但它们有十分相似的三级结构的活性中心和相同的催化功能。RR分子中包含2个变构位点,即酶活性中心和底物特异结合位点。活性中心通过生物有机自由基的作用催化核糖核苷酸还原;底物特异结合位点通过变构作用调控4种dNTPs在细胞内的平衡。因此,该酶不仅是研究DNA合成与修复、细胞增殖与分化及癌症的治疗与抗癌药物开发的重要靶点,同时也是研究酶的结构与功能以及酶的催化机理等的重要工具。本文总结了该酶的种类与分布、结构特征、催化机理及作为抗癌药物开发靶点等方面的研究进展。

植物肉桂酰辅酶A还原酶(CCR)基因的研究进展

植物体内通过公共苯丙烷途径而进入木质素特异途径来合成木质素,这条代谢途径涉及到许多酶的参与,其中肉桂酰辅酶A还原酶(cinnamoyl-CoAreductase,CCR)是木质素特异途径的第一个关键酶,可催化3种羟基肉桂酸的CoA酯的还原反应,生成相应的肉桂醛。因此人们认为此酶可能对木质素合成途径的碳流具有潜在的调控作用,对木质素单体的生物合成起着重要作用。本文主要综述了CCR在木质素生物合成途径中的地位、CCR的分布、酶的提取和基本特性、CCR基因的克隆进展、CCR基因的转录特点、CCR启动子研究情况、转基因植物中表达抑制CCR基因的生物学效应等,并展望了CCR基因研究对于植物木质素研究、植物抗病和抗逆性研究、作物品质改良以及植被保护研究的意义。

晚期非小细胞肺癌RRM1表达与吉西他滨疗效的相关性分析

目的探讨晚期非小细胞肺癌(non-small cell lung cancer,NSCLC)组织中核苷酸还原酶M1(RRM1)的表达水平与吉西他滨联合顺铂化疗疗效及预后的相关性。方法通过免疫组织化学法检测60例晚期NSCLC患者肺组织中RRM1蛋白表达水平,并与患者的临床特征、吉西他滨联合顺铂化疗的疗效及预后的关系进行分析。结果 RRM1的表达在不同性别间差异有统计学意义(P<0.05);在不同年龄、组织学类型及分期间差异无统计学意义(P>0.05)。RRM1低表达组的化疗有效率(57.7%)及疾病控制率(69.2%)均高于高表达组(29.4%,35.3%)(P<0.05)。在对生存期的分析中发现RRM1低表达组的生存期(18月)及无疾病进展期(6月)均明显长于高表达组(13月,4月)(P<0.05),1年生存率(69.2%)及2年生存率(23.1%)均高于高表达组(58.8%,3%)(P<0.05)。结论晚期非小细胞肺癌组织中RRM1低表达的患者对吉西他滨联合顺铂化疗反应的有效率更高,生存期更长,是独立的预后因素。这将有助于筛选适合接受吉西他滨联合顺铂进行一线化疗的患者。

有氧运动对线粒体质子跨膜转运及核糖核苷二磷酸还原酶的影响

本实验通过对有氧运动训练 (无负重游泳 6 0分钟 /天 ,7天 )大鼠游泳运动后的骨骼肌、心肌线粒体质子跨膜转运能力及核糖核苷二磷酸还原酶活性的测定 ,发现有氧运动训练的大鼠在定量运动负荷后 (6 0分钟无负重游泳 ) ,骨骼肌线粒体的质子跨膜转运能力显著提高 (P <0 0 5 ) ,以及线粒体的核糖核苷二磷酸还原酶活性明显高于对照组 (未经训练之大鼠 ,P <0 0 0 1)。而心肌线粒体的以上两项指标变化不甚明显。结果显示 ,骨骼肌线粒体对有氧运动训练的适应过程与其质子跨膜转运能力的提高及核糖核苷二磷酸还原酶活性增加有关。提示骨骼肌线粒体在慢性高氧化磷酸化状态刺激下 ,可能同时导致DNA生物合成的增加 ,即线粒体基因组对其功能变化产生应答反应。心肌线粒体的运动适应过程与骨骼肌线粒体不尽相同。

肺癌患者RRM1(-37)位点基因多态性及其与临床相关性的研究

背景与目的吉西他滨是目前治疗非小细胞肺癌(NSCLC)的一线药物。研究表明作为吉西他滨作用靶点的核苷酸还原酶亚单位M1(RRM1),其启动子区域的基因多态性可以影响吉西他滨对非小细胞肺癌患者的疗效。本研究旨在建立一种简便和高特异性的方法,检测RRM1(-37)位点的基因多态性,并以此方法分析RRM1(-37)位点A/C基因型与吉西他滨治疗NSCLC疗效的相关性。方法收集110例肺癌患者和40例健康人的外周血,提取基因组DNA,以RRM1基因的启动子区域为目的基因,合成野生型引物WF、突变型引物TF和共同的下游引物R。利用DNA荧光嵌入染料SYBR Green I进行荧光PCR扩增,对PCR产物进行熔解曲线分析以确定基因型。分析RRM1(-37)位点基因多态性与患者的一般状态、接受吉西他滨治疗的疗效及生存时间的关系。结果110例肺癌患者和40例健康人中A/A等位基因频率分别为32%和30%,两组人群在RRM1(-37)位点基因分布频率上无统计学差异,RRM1(-37)位点的基因多态性与肺癌患者的性别、病理类型及临床分期无相关性(P>0.05),且与肺癌患者接受吉西他滨治疗的疗效及生存时间无相关性(P>0.05)。结论本研究建立的引物特异性实时荧光PCR法可对RRM1(-37)位点进行准确的基因分型。

植物体内一氧化氮合成途径研究进展

一氧化氮(NO)作为一种气体信号分子,在植物生理过程中发挥重要作用,它参与调节植物的生长、发育及对外界环境的应激反应。植物体内主要通过酶催化途径和非酶催化途径合成NO。酶催化途径合成NO的主要酶包括一氧化氮合酶(nitric oxide synthase,NOS)和硝酸还原酶(nitrate reductase,NR),以及在某些植物的特定组织或器官或在特殊环境条件下存在的一氧化氮氧化还原酶(nitric oxide oxidoreductase,Ni-NOR)和黄嘌呤氧化还原酶(xanthine oxidoreductase,XOR)。非酶催化合成途径主要是在酸性和还原剂存在条件下将亚硝酸盐还原成NO。该文主要结合研究方法,综述了植物体内NO合成途径的研究进展,为植物体内NO信号的作用机理的深入研究提供信息资料。

ERCC1、RRM1表达对肺癌患者术后吉西他滨联合顺铂化疗生存趋势的影响

背景与目的肺癌化疗疗效与肿瘤的基因表达有关,本研究拟探讨ERCC1、RRM1表达与非小细胞肺癌术后吉西他滨联合顺铂(GP)辅助化疗预后的关系。方法随访57例临床Ⅱ-Ⅳ期接受手术治疗的非小细胞肺癌患者,其中术后接受2周期以上化疗者39例(化疗组),未化疗者18例(未化疗组)。采用免疫组化法检测ERCC1、RRM1表达,Cox回归分析筛选影响预后的独立危险因子,Kaplan-Meier生存曲线分析比较各组患者的中位生存时间。结果Cox回归分析显示手术彻底程度、术后辅助化疗与否、ERCC1表达水平为影响术后生存时间的独立危险因子。ERCC1低表达组中化疗组和未化疗组中位生存期分别为23个月和21个月(P=0.088),ERCC1高表达组中化疗组和未化疗组中位生存期分别为42个月和12个月(P=0.018)。RRM1低表达组中化疗组和未化疗组中位生存期分别为42个月和22个月(P=0.010),RRM1高表达组中化疗组和未化疗组中位生存期分别为28个月和21个月(P=0.092)。结论ERCC1高表达、RRM1低表达的非小细胞肺癌患者更能从术后吉西他滨联合顺铂的化疗中受益。