Mechanistic similarity and diversity among the guanidine-modifying members of the pentein superfamily

The pentein superfamily is a mechanistically diverse superfamily encompassing both noncatalytic proteins and enzymes that catalyze hydrolase, dihydrolase and amidinotransfer reactions on guanidine substrates. Despite generally low sequence identity, they possess a conserved structural fold and display common mechanistic themes in catalysis. The structurally characterized catalytic penteins possess a conserved core of residues that include a Cys, His and two polar, guanidine-binding residues. All known catalytic penteins use the core Cys to attack the substrate's guanidine moiety to form a covalent thiouronium adduct and all cleave one or more of the guanidine C―N bonds. The mechanistic information compiled to date supports the hypothesis that this superfamily may have evolved divergently from a catalytically promiscuous ancestor.     

ADMA induces monocyte adhesion via activation of chemokine receptors in cultured THP-1 cells

Asymmetric dimethylarginine (ADMA), an endogenous NOS inhibitor, is also an important inflammatory factor contributing to the development of atherosclerosis (AS). The present study was to test the effect of ADMA on angiotensin (Ang) II-induced monocytic adhesion. Human monocytoid cells (THP-1) or isolated peripheral blood monocyte cells (PBMCs) were incubated with Ang II (10⁻⁶ M) or exogenous ADMA (30 μM) for 4 or 24 h in the absence or presence of losartan or antioxidant PDTC. In cultured THP-1 cells, Ang II (10⁻⁶ M) for 24 h elevated the level of ADMA in the medium, upregulated the protein expression of protein arginine methyltransferase (PRMT) and decreased the activity of dimethylarginine dimethylaminohydrolase (DDAH). Both of Ang II and ADMA increased monocytic adhesion to human umbilical vein endothelial cells (HUVECs), elevated the levels of monocyte chemoattractant protein (MCP)-1, interleukin (IL)-8 and tumor necrosis factor (TNF)-α and upregulated CCR₂ and CXCR₂ mRNA expression, concomitantly with increase in reactive oxygen species (ROS) generation and activation of nuclear factor (NF)-κB. Pretreatment with losartan (10 μM) or PDTC (10 μM) abolished the effects mediated by Ang II or ADMA. In isolated PBMCs from healthy individuals, ADMA upregulated the expression of CXCR₂ mRNA, which was attenuated by losartan (10 μM), however, ADMA had no effect on surface protein expression of CCR₂. The present results suggest that ADMA may be involved in monocytic adhesion induced by Ang II via activation of chemokine receptors by ROS/NF-κB pathway.     

DDAH2启动子区-1150C/A多态性与中国汉族人群冠心病的遗传易感性研究

目的:研究DDAH2启动子区-1150 C/A rs805304多态性与中国汉族人群冠心病之间的相关性。方法:应用限制性片段长度多态性聚合酶链反应(PCR-RFLP)的分析方法,对381例冠心病患者和629例健康人群中DDAH2基因A-1150C rs805304多态进行基因分型。结果:病例组和对照组A-1150C rs805304位点基因型分布均符合Hardy-Wenberg平衡;两组间A-1150C位点基因型间无显著性的差异(P=0.34);病例组和对照组A-1150C位点的等位频率分布也无显著的差别,但是在冠心病病例中,A等位频率有低于C等位频率的趋势(P=0.069)。结论:DDAH2启动子区-1150 C/A rs805304多态性与中国汉族人群冠心病的发病不相关。     

Assessment of serum levels of asymmetric dimethylarginine,symmetric dimethylarginine and l-arginine in coronary artery disease

Serum asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), l-arginine, and C-reactive protein (hsCRP) levels were assessed in 100 Egyptian male 35–50-year-old patients with coronary artery disease (CAD), classified into: patients under conservative medical treatment, patients directed for percutaneous coronary interventions, patients directed for coronary artery bypass graft operation and patients suffering from acute myocardial infarction. Age- and sex-matched controls (n?=?100) were included. Correlation between serum levels of biomarkers and dimethylarginine dimethylaminohydrolase-2 (DDAH-2) genotypes was studied. No association between biomarkers and carriage of the specific DDAH2 SNP2 (-449C/G, rs805305) genotype was detected. Further studies are required to confirm the contribution of the biomarkers in the predisposition of CAD.     

非对称二甲基精氨酸水解酶的表达纯化及其酶学性质的研究

非对称二甲基精氨酸水解酶(dimethylarginine Dimethylaminohydrolase,DDAH)是酶学循环法检测早期急性心肌梗塞(acute myocardial infarction,AMI)的生物标记物——非对称二甲基精氨酸(asymmetric dimethylarginine,ADMA)的重要工具酶.为获得高活性DDAH,从绿脓杆菌的基因组中扩增目的基因,构建高效表达DDAH的重组菌E.coli BL 21(pET-28a-DDAH).该菌的可溶性DDAH表达量达100mg/L,经超声破碎后的上清液通过镍柱纯化,可获得纯度达到95％以上的重组DDAH.Q柱的精制可提高它的稳定性,使其能够在常温下长期保持酶活.该重组酶的单位酶活,Km值和Vmax分别为0.5U/mg,3.04 mM和8.07mM/h.最适反应温度和pH分别为35℃和pH =6,在10℃～40℃和pH5.0～ pH9.0的范围内稳定.该重组酶可形成多聚体,但并不影响酶活.最后,利用发酵罐扩大生产规模,有望进行克级生产,为新型ADMA检测试剂盒的开发和药物筛选模型提供材料基础.     

Determine exogenous human DDAH2 gene function in rabbit bone marrow–derived endothelial progenitor cells in vitro

The in vitro amplification of endothelial progenitor cells (EPCs) is an important method because of its role in gene transferring and regenerative medicine. In this study, we isolated rabbit bone marrow–derived EPCs to further manipulation and overexpression of dimethylarginine dimethylaminohydrolase (DDAH) in EPCs. Isolated EPCs were cultured, expanded in endothelial basal medium. Morphology of EPCs and expression levels of surface markers detected using immunocytochemistry staining and through the use of flow cytometery. Endothelial progenitor cells were transfected with plasmid vectors expressing human DDAH2 (DDAH2‐EPCs). Three days after gene transfer, positive transfected‐EPCs proliferation and DDAH activity were assayed. We observed colonies conformation and endothelium‐like morphology gradually in the third week of culture. Characterization results revealed positive expression of EPC surface markers CD106, Flk‐1, vWF, and CD34 using few identification techniques. Overexpression of DDAH2 increased citrulline production after 96 hours of transfection, 235.34 ± 0.69 vs 95.26 ± 5.76 ng/mL; P = .023. These results suggest that cell population with EPC characteristics can be simply isolated from rabbit bone marrow and successfully engineered to overexpress exogenous gene. In this study, we offer a feasible method to isolate and identify EPCs from bone marrow. In addition, an efficient transfection with a plasmid vector (without risk of interference) can be constructed a hybrid structure with EPC and DDAH2 gene to examine their function in vitro.