Differential Metabolism of Organic Nitrates by Aldehyde Dehydrogenase 1a1 and 2: Substrate Selectivity, Enzyme Inactivation, and Active Cysteine Sites
Journal Title: The AAPS Journal - Year 2011, Vol 13, Issue 4
Abstract
Organic nitrate vasodilators (ORN) exert their pharmacologic effects through the metabolic release of nitric oxide (NO). Mitochondrial aldehyde dehydrogenase (ALDH2) is the principal enzyme responsible for NO liberation from nitroglycerin (NTG), but lacks activity towards other ORN. Cytosolic aldehyde dehydrogenase (ALDH1a1) can produce NO from NTG, but its activity towards other ORN is unknown. Using purified enzymes, we showed that both isoforms could liberate NO from NTG, isosorbide dinitrate (ISDN), and nicrorandil, while only ALDH1a1 metabolized isosorbide-2-mononitrate and isosorbide-5-mononitrate (IS-5-MN). Following a 10-min incubation with purified enzyme, 0.1 mM NTG and 1 mM ISDN potently inactivated ALDH1a1 (to 21.9% ± 11.1% and 0.44% ± 1.04% of control activity, respectively) and ALDH2 (no activity remaining and 4.57% ± 7.92% of control activity, respectively), while 1 mM IS-5-MN exerted only modest inactivation of ALDH1a1 (reduced to 89% ± 4.3% of control). Cytosolic ALDH in hepatic homogenates incubated at the vascular EC50 concentrations of ORN was inactivated by NTG (to 45.1% ± 8.1% of control activity) while mitochondrial ALDH was inactivated by NTG and nicorandil (to 68.2% ± 10.0% and 78.7% ± 19.8% of control, respectively). Via site-directed mutagenesis, the active sites of ORN metabolism of ALDH2 (Cys-319) and ALDH1a1 (Cys-303) were found to be identical to those responsible for their dehydrogenase activity. Cysteine-302 of ALDH1a1 and glutamate-504 of ALDH2 were found to modulate the rate of ORN metabolism. These studies provide further characterization of the substrate selectivity, inactivation, and active sites of ALDH2 and ALDH1a1 toward ORN.
Authors and Affiliations
Pei-Suen Tsou, Nathaniel A. Page, Sean G. Lee, Sun Mi Fung, Wing Ming Keung, Ho-Leung Fung
Keywords
Related Articles
- EP ID EP681340
- DOI 10.1208/s12248-011-9295-4
- Views 46
- Downloads 0
PEGylation of a Factor VIII–Phosphatidylinositol Complex: Pharmacokinetics and Immunogenicity in Hemophilia A Mice
Hemophilia A is an X-linked bleeding disorder caused by the deficiency of factor VIII (FVIII). Exogenous FVIII is administered therapeutically, and due to a short half-life, frequent infusions are often required. Fifteen...
Triple Recycling Processes Impact Systemic and Local Bioavailability of Orally Administered Flavonoids
The online version of this article (doi:10.1208/s12248-015-9732-x) contains supplementary material, which is available to authorized users.
Challenges and Opportunities in Achieving Bioequivalence for Fixed-Dose Combination Products
Fixed-dose combination (FDC) products are becoming a popular treatment option because of increased patient compliance and convenience, improved clinical effectiveness, and reduced cost to the patient, among several other...
Development of a GC-MS Assay for the Determination of Fentanyl Pharmacokinetics in Rabbit Plasma after Sublingual Spray Delivery
Fentanyl free base was kindly supplied by Insys Therapeutics, Inc (Mundelein, IL), fentanyl citrate and sufentanil free base were obtained from Mallinckrodt Chemicals (St. Louis, MO). 1-Chlorobutane was purchased from Ac...
Structural and Activity Profile Relationships Between Drug Scaffolds
The online version of this article (doi:10.1208/s12248-015-9737-5) contains supplementary material, which is available to authorized users.