Predicting the catalytic sites of isopenicillin N synthase (IPNS) related non-haem iron-dependent oxygenases and oxidases (NHIDOX) through a structural superimposition and molecular docking approach

Isopenicillin N synthase (IPNS) related Non-haem iron-dependent oxygenases and oxidases (NHIDOX) demonstrated a striking structural conservativeness, even with low protein sequence homology. It is evident that these enzymes have an architecturally similar catalytic centre with active ligands lining the reactive pocket. Deacetoxycephalosporin C synthase (DAOCS), isopenicillin N synthase (IPNS), deacetylcephalosporin C synthase (DACS), clavaminate synthase 1 and 2 (CAS1 and 2) are important bacterial enzymes that catalyze the formation of β-lactam antibiotics belonging to this enzyme family. Most plant enzyme members within this subfamily namely flavonol synthase (FLS), leucoanthocyanidin dioxygenase (LDOX), anthocyanidin synthase (ANS), 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO), gibberellin 20-oxidase (G20O), desacetoxyvindoline-4-hydroxylase (D4H), flavanone 3β-hydroxylase (F3H), and hyoscyamine 6β-hydroxylase (H6H) are involved in catalyzing the biosyntheses of plant secondary metabolites. With the advancement of protein structural analysis software, it is possible to predict the catalytic sites of protein that shared a structural resemblance. By exploiting the superimposition model of DAOCS-IPNS, DAOCS-IPNS-CAS, G20O-LDOX, FLS-LDOX, ACCO-LDOX, D4H-LDOX, F3H-LDOX and H6H-LDOX model; a computational protocol for predicting the catalytic sites of proteins is now made available. This study shows that without the crystallized or nuclear magnetic resonance (NMR) structures of most NHIDOX enzyme, the plausible catalytic sites of protein can be forecasted using this structural bioinformatics approach.Keywords: Enzyme, catalytic sites, isopenicillin N synthase, ligand

Elucidating the mechanism of the immunosuppressive action of PX3.102, the active molecule from a decoction of Chinese herbs

Master'sMASTER OF SCIENC

Pharmacokinetic Modeling of Plasma and Intracellular Concentrations of Raltegravir in Healthy Volunteers▿

Raltegravir is a potent inhibitor of HIV integrase. Persistently high intracellular concentrations of raltegravir may explain sustained efficacy despite high pharmacokinetic variability. We performed a pharmacokinetic study of healthy volunteers. Paired blood samples for plasma and peripheral blood mononuclear cells (PBMCs) were collected predose and 4, 8, 12, 24, and 48 h after a single 400-mg dose of raltegravir. Samples of plasma only were collected more frequently. Raltegravir concentrations were determined using liquid chromatography-mass spectrometry. The lower limits of quantitation for plasma and PBMC lysate raltegravir were 2 nmol/liter and 0.225 nmol/liter, respectively. Noncompartmental analyses were performed using WinNonLin. Population pharmacokinetic analysis was performed using NONMEM. Six male subjects were included in the study; their median weight was 67.4 kg, and their median age was 33.5 years. The geometric mean (GM) (95% confidence interval shown in parentheses) maximum concentration of drug (Cmax), area under the concentration-time curve from 0 to 12 h (AUC0–12), and area under the concentration-time curve from 0 h to infinity (AUC0–∞) for raltegravir in plasma were 2,246 (1,175 to 4,294) nM, 10,776 (5,770 to 20,126) nM · h, and 13,119 (7,235 to 23,788) nM · h, respectively. The apparent plasma raltegravir half-life was 7.8 (5.5 to 11.3) h. GM intracellular raltegravir Cmax, AUC0–12, and AUC0–∞ were 383 (114 to 1,281) nM, 2,073 (683 to 6,290) nM · h, and 2,435 (808 to 7,337) nM · h (95% confidence interval shown in parentheses). The apparent intracellular raltegravir half-life was 4.5 (3.3 to 6.0) h. Intracellular/plasma ratios were stable for each patient without significant time-related trends over 48 h. Population pharmacokinetic modeling yielded an intracellular-to-plasma partitioning ratio of 11.2% with a relative standard error of 35%. The results suggest that there is no intracellular accumulation or persistence of raltegravir in PBMCs