A Comprehensive Study of the Active Site Residues of DT-Diaphorase: Rational Design of Benzimidazolediones as DT-Diaphorase Substrates
摘要:
A series of quinone substrates were modeled into the active site of human DT-diaphorase and minimized. Correlation of these models with the substrate specificity k(cat)/K-m provided insights into the structural requirements of quinone substrates. The W105, F106, and H194 residues can influence the position of the quinone substrate in the active site resulting in formation of one of the two possible Michael anions resulting from hydride transfer from FADH(2). Electron withdrawing groups on the substrate can stabilize these anions resulting in excellent substrate specificity. Inspection of models indicated that the W-105 and F-106 residues form parallel walls that will accommodate large polycyclic substrates. Thus excellent polycyclic substrates of DT-diaphorase were designed. However, the placement of tetrahedral centers on these polycyclic substrates interfered with the W-105 and the F-106 residues resulting in their exclusion from the active site. The histidine (H194) residue permits recognition of substrate enantiomers as a result of hydrogen bonding interactions. As a result of this study, it will be possible to design poor to excellent substrates of DT-diaphorase and take advantage of varying levels of this enzyme in histologically different cancers.
One-pot double intramolecular homolytic aromatic substitution routes to dialicyclic ring fused imidazobenzimidazolequinones and preliminary analysis of anticancer activity
作者:Vincent Fagan、Sarah Bonham、Michael P. Carty、Fawaz Aldabbagh
DOI:10.1039/c003511d
日期:——
Bu3SnH/1,1′-azobis(cyclohexanecarbonitrile) (ACN)-mediated five, six, and seven-membered double alkyl radical cyclizations onto imidazo[5,4-f]benzimidazole and imidazo[4,5-f]benzimidazole are described. The quinone derivatives evaluated show selective toxicity towards human cervical (HeLa) and prostate (DU145) cancer cell lines (with negligible toxicity towards a normal human cell line, GM00637). Only the Fremy oxidation of the 6-aminoimidazo[5,4-f]benzimidazole gave iminoquinone, which showed high specificity towards the prostate cancer cell line (DU145).