The substrate specificity of a purified kidney neutral endopeptidase was studied. The endopeptidase hydrolyzed a variety of biologically active peptides, such as angiotensins (angiotensins I, II and III), bradykinins (bradykinin, Lys-bradykinin, Met-Lys-bradykinin and des-9Arg-bradykinin), enkephalins (Leu-enkephalin and Met-enkephalin), neurotensin and substance P, and was found to cleave only the bonds at the amino side of hydrophobic amino acids in the peptides. However, when a hydrophobic amino acid was present at the C-terminus or at the position adjacent to the N-terminus, the bond of the hydrophobic residue was not cleaved. In further studies on the degradation of a series of homo-oligopeptides, the enzyme appeared to hydrolyze those consisting of at least a tetrapeptide unit of hydrophobic amino acids such as Ala and Phe. The specificity of the membrane-bound neutral endopeptidase from rat kidney indicated by these results can be summarized as follows : the enzyme requires at least a tetrapeptide unit for hydrolysis, and cleavage occurs only at the amino side of a hydrophobic amino acid, when one is present at the third position of the tetrapeptide unit.
Characterization of a Hemoglobin Adduct from Ethyl Vinyl Ketone Detected in Human Blood Samples
作者:Henrik Carlsson、Hitesh V. Motwani、Siv Osterman Golkar、Margareta Törnqvist
DOI:10.1021/acs.chemrestox.5b00287
日期:2015.11.16
article describes the characterization of one of these adducts, which was identified as the adduct from ethyl vinyl ketone (EVK). The mean adduct level was 40 ± 12 pmol/g Hb in 12 human blood samples; adduct levels from acrylamide (AA) and methyl vinyl ketone (MVK) were quantified for comparison. Using l-valine p-nitroanilide (Val-pNA), introduced as a model of the N-terminal valine, the rate of formation
亲电试剂具有与蛋白质和DNA的亲核位点形成加合物的能力。因此,内部暴露于此类化合物会产生毒性作用。通过质谱方法通过质谱法对加合物的筛选提供了检测组织中存在的未知亲电试剂的可能性。以前,我们采用非靶向药物治疗人类血液中血红蛋白(Hb)中N末端缬氨酸的19种未知加合物。本文介绍了其中一种加合物的表征,该加合物被鉴定为来自乙基乙烯基酮(EVK)的加合物。在12个人体血液样本中,平均加合物水平为40±12 pmol / g Hb。定量比较丙烯酰胺(AA)和甲基乙烯基酮(MVK)的加合物含量。使用l-缬氨酸对硝基苯胺(Val-p NA),作为N末端缬氨酸的模型,研究了EVK加合物的形成速率,并在37°C下确定了200 M –1 h –1的速率常数。在血液中,反应速度太快而无法测量,EVK的半衰期小于1分钟。用AA和MVK进行的并行实验表明,两种乙烯基酮的反应速度比AA快2×10 3倍。发现EVK-Hb加合物不稳定,半衰期为7
Discovery of Novel <i>N</i>-(4-Hydroxybenzyl)valine Hemoglobin Adducts in Human Blood
作者:Amanda Degner、Henrik Carlsson、Isabella Karlsson、Johan Eriksson、Suresh S. Pujari、Natalia Y. Tretyakova、Margareta Törnqvist
DOI:10.1021/acs.chemrestox.8b00173
日期:2018.12.17
380 ± 160 pmol/g Hb. Two possible routes of 4-OHBnVal adduct formation are proposed using two different precursor electrophiles: 4-quinone methide (4-QM) and 4-hydroxybenzaldehyde (4-OHBA). We found that 4-QM reacts rapidly with valine to form the 4-OHBn-Val adduct; however, the quinonemethide is unstable under physiological conditions due to hydrolysis. It was shown that 4-OHBA forms reversible Schiff
人类会暴露于我们饮食和环境中或作为正常生理过程一部分的内源性形成的各种亲电子化合物中。这些亲电试剂可以修饰蛋白质和DNA的亲核位点,以形成共价加合物。近来,已经开发出有力的非靶向的成瘾方法,用于系统筛选人血中的这些加合物。我们较早的非靶向药物治疗研究在人体血液中的血红蛋白(Hb)中检测到19种未知的N末端缬氨酸加合物。现在我们描述这些加合物之一的完整表征,其对应于在Hb中向N末端缬氨酸添加4-羟基苄基(4-OHBn)基团以形成N(4-羟基苄基)缬氨酸(4-OHBn-Val )。通过比较加合物的准确质量,HPLC保留时间,并将MS / MS碎片化为化学合成制备的真实标准品。在12个人体血液样本中,平均4-OHBn-Val加合物浓度估计为380±160 pmol / g Hb。提出了使用两种不同的前体亲电试剂形成4-OHBnVal加合物的两种可能途径:4-醌甲基化物(4-QM)和4-羟基苯甲醛
Studies on the β-Turn of Peptides. VII. Syntheses and Antibiotic Activities of Gramicidin S Analogs with L-Pro-L-Asn or L-Pro-D-Ala Sequence at the β-Turn Part
作者:Kazuki Sato、Ukon Nagai
DOI:10.1246/bcsj.56.3329
日期:1983.11
Two analogs of gramicidinS (GS), [L-Pro4,4′, L-Asn5,5′]-GS (10a) and [L-Pro4,4′, D-Ala5,5′]-GS were synthesized to investigate the possibility of replacing the β-turn part of GS by a different type of β-turn keeping the biological activity. For the synthesis of 10a, three procedures were examined and satisfactory results were obtained by the active ester method applied to cyclization of linear decapeptide
a primary amine group and two amide units have been developed and evaluated in the directasymmetric intermolecular aldolreaction of 4-nitrobenzaldehyde and cyclohexanone. When 2,4-dinitrophenol (DNP) was used as an acidic additive, the catalyzedreactions of various aldehydes and ketones gave the corresponding aldol products with moderate to high enantioselectivities (up to 95%) and diastereoselectivities