Biomedical subjects

Yuan-Ping Pang

Publications and source records attributed to Yuan-Ping Pang.

24 records · Page 2Linked to original sources

PubMed2003

Rational design of alkylene-linked bis-pyridiniumaldoximes as improved acetylcholinesterase reactivators.

To improve the potency of 2-pralidoxime (2-PAM) for treating organophosphate poisoning, we dimerized 2-PAM and its analogs according to Wilson's pioneering work and the 3D structure of human acetylcholinesterase (hAChE) inactivated by isoflurophate. 1,7-Heptylene-bis-N,N'-syn-2-pyridiniumaldoxime, the most potent of the alkylene-linked dimeric reactivators, was readily synthesized using bistriflate and is 100 times more potent than 2-PAM in reactivating hAChE poisoned by isoflurophate. Experimental and computational studies confirm that 2-PAM in its biologically active form adopts the syn-I configuration. Further, they suggest that the improved performance of dimeric oximes is conferred by two-site binding with one oxime pointing toward the diisopropyl ester at the catalytic site of hAChE and the other anchored at the peripheral site. This type of binding may induce a conformational change in the acyl pocket loop which modulates the catalytic site via a domino effect.

Acetylcholinesterase↗

PubMed2002

The antiangiogenic activity of cleaved high molecular weight kininogen is mediated through binding to endothelial cell tropomyosin.

Conformationally altered proteins and protein fragments derived from the extracellular matrix and hemostatic system may function as naturally occurring angiogenesis inhibitors. One example of such a protein is cleaved high molecular weight kininogen (HKa). HKa inhibits angiogenesis by inducing apoptosis of proliferating endothelial cells, effects mediated largely by HKa domain 5. However, the mechanisms underlying the antiangiogenic activity of HKa have not been characterized, and its binding site on proliferating endothelial cells has not been defined. Here, we report that the induction of endothelial cell apoptosis by HKa, as well as the antiangiogenic activity of HKa in the chick chorioallantoic membrane, was inhibited completely by antitropomyosin monoclonal antibody TM-311. TM-311 also blocked the high-affinity Zn2+-dependent binding of HKa to both purified tropomyosin and proliferating endothelial cells. Confocal microscopic analysis of endothelial cells stained with monoclonal antibody TM-311, as well as biotin labeling of cell surface proteins on intact endothelial cells, revealed that tropomyosin exposure was enhanced on the surface of proliferating cells. These studies demonstrate that the antiangiogenic effects of HKa depend on high-affinity binding to endothelial cell tropomyosin.

Allantois↗

PubMed2002

Cocaine metabolism accelerated by a re-engineered human butyrylcholinesterase.

Plasma butyrylcholinesterase (BChE) is important in the metabolism of cocaine, but natural human BChE has limited therapeutic potential for detoxication because of low catalytic efficiency with cocaine. Here we report pharmacokinetics of cocaine in rats treated with A328W/Y332A BChE, an excellent cocaine hydrolase designed with the aid of molecular modeling. Compared with wild-type BChE, this enzyme hydrolyzes cocaine with 40-fold improved k(cat) (154 min(-1) versus 4.1 min(-1)) and only slightly increased K(M) (18 microM versus 4.5 microM). In rats given this hydrolase (3 mg/kg i.v.) 10 min before cocaine challenge (6.8 mg/kg i.v.), cocaine half-life was reduced from 52 min to 18 min. Mirroring the reductions of plasma cocaine were large increases in benzoic acid, a product of BChE-mediated cocaine hydrolysis. All other pharmacokinetic parameters confirmed a large, dose-dependent acceleration of cocaine removal by the injected cocaine hydrolase. These results show that A328W/Y332A, an efficient cocaine hydrolase in vivo as well as in vitro, might promote cocaine detoxication in a clinical setting.

Amino Acid Substitution↗

PubMed2002

Re-engineering butyrylcholinesterase as a cocaine hydrolase.

To address the problem of acute cocaine overdose, we undertook molecular engineering of butyrylcholinesterase (BChE) as a cocaine hydrolase so that modest doses could be used to accelerate metabolic clearance of this drug. Molecular modeling of BChE complexed with cocaine suggested that the inefficient hydrolysis (k(cat) = 4 min(-1)) involves a rotation toward the catalytic triad, hindered by Tyr332. To eliminate rotational hindrance and retain substrate affinity, we introduced two amino acid substitutions (Ala328Trp/Tyr332Ala). The resulting mutant BChE reduced cocaine burden in tissues, accelerated plasma clearance by 20-fold, and prevented cocaine-induced hyperactivity in mice. The enzyme's kinetic properties (k(cat) = 154 min(-1), K(M) = 18 microM) satisfy criteria suggested previously for treating cocaine overdose (k(cat) >120 min(-1), K(M) < 30 microM). This success demonstrates that computationally guided mutagenesis can generate functionally novel enzymes with clinical potential.

Alanine↗

PubMed2001

EUDOC: a computer program for identification of drug interaction sites in macromolecules and drug leads from chemical databases.

The completion of the Human Genome Project, the growing effort on proteomics, and the Structural Genomics Initiative have recently intensified the attention being paid to reliable computer docking programs able to identify molecules that can affect the function of a macromolecule through molecular complexation. We report herein an automated computer docking program, EUDOC, for prediction of ligand-receptor complexes from 3D receptor structures, including metalloproteins, and for identification of a subset enriched in drug leads from chemical databases. This program was evaluated from the standpoints of force field and sampling issues using 154 experimentally determined ligand-receptor complexes and four "real-life" applications of the EUDOC program. The results provide evidence for the reliability and accuracy of the EUDOC program. In addition, key principles underlying molecular recognition, and the effects of structural water molecules in the active site and different atomic charge models on docking results are discussed. Copyright 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1750-1771, 2001

Journal Article↗

PubMedDate not supplied

Improved loading and cleavage methods for solid-phase synthesis using chlorotrityl resins: synthesis and testing of a library of 144 discrete chemicals as potential farnesyltransferase inhibitors.

The use of chlorotrityl resins for the immobilization of amines is sometimes deterred by the lengthy process of loading the reactants on the resins and product decomposition caused by the reactive chlorotrityl group in the presence of 1% TFA as a cleavage agent. Here, we report improved methods developed for selective and efficient loading of aminobenzoic acid derivatives on chlorotrityl resins and for cleavage of aniline-containing products from the resins without decomposition. These methods led to the synthesis of a library of 144 discrete chemicals as potential farnesyltransferase inhibitors (FTIs) using IRORI's radio-frequency-encoded sorting technique and to the study of the applicability of the bivalence approach to the development of FTIs.

Amino Acids↗