title: Bioactivation of nitroglycerin by purified mitochondrial and cytosolic aldehyde dehydrogenases.
abstract: Metabolism of nitroglycerin (GTN) to 1,2-glycerol dinitrate (GDN) and nitrite by mitochondrial aldehyde dehydrogenase (ALDH2) is essentially involved in GTN bioactivation resulting in cyclic GMP-mediated vascular relaxation. The link between nitrite formation and activation of soluble guanylate cyclase (sGC) is still unclear. To test the hypothesis that the ALDH2 reaction is sufficient for GTN bioactivation, we measured GTN-induced formation of cGMP by purified sGC in the presence of purified ALDH2 and used a Clark-type electrode to probe for nitric oxide (NO) formation. In addition, we studied whether GTN bioactivation is a specific feature of ALDH2 or is also catalyzed by the cytosolic isoform (ALDH1). Purified ALDH1 and ALDH2 metabolized GTN to 1,2- and 1,3-GDN with predominant formation of the 1,2-isomer that was inhibited by chloral hydrate (ALDH1 and ALDH2) and daidzin (ALDH2). GTN had no effect on sGC activity in the presence of bovine serum albumin but caused pronounced cGMP accumulation in the presence of ALDH1 or ALDH2. The effects of the ALDH isoforms were dependent on the amount of added protein and, like 1,2-GDN formation, were sensitive to ALDH inhibitors. GTN caused biphasic sGC activation with apparent EC(50) values of 42 +/- 2.9 and 3.1 +/- 0.4 microm in the presence of ALDH1 and ALDH2, respectively. Incubation of ALDH1 or ALDH2 with GTN resulted in sustained, chloral hydrate-sensitive formation of NO. These data may explain the coupling of ALDH2-catalyzed GTN metabolism to sGC activation in vascular smooth muscle.
authors.affiliation: Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, Graz, Austria.
authors.forename: Matteo
authors.initials: M
authors.lastname: Beretta
authors.forename: Karl
authors.initials: K
authors.lastname: Gruber
authors.forename: Alexander
authors.initials: A
authors.lastname: Kollau
authors.forename: Michael
authors.initials: M
authors.lastname: Russwurm
authors.forename: Doris
authors.initials: D
authors.lastname: Koesling
authors.forename: Walter
authors.initials: W
authors.lastname: Goessler
authors.forename: Wing Ming
authors.initials: WM
authors.lastname: Keung
authors.forename: Kurt
authors.initials: K
authors.lastname: Schmidt
authors.forename: Bernd
authors.initials: B
authors.lastname: Mayer
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000737:chemistry*; D000080924:Aldehyde Dehydrogenase 1 Family; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D002384:Catalysis; D002417:Cattle; D006152:Cyclic GMP / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry*; D008928:Mitochondria / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000201:enzymology; D005996:Nitroglycerin / Q000031:analogs & derivatives / Q000737:chemistry*; D020033:Protein Isoforms; D050697:Retinal Dehydrogenase; D012709:Serum Albumin / Q000737:chemistry
chemical_list: D007527:Isoenzymes; D020033:Protein Isoforms; D012709:Serum Albumin; C014509:dinitroglycerol; D000080924:Aldehyde Dehydrogenase 1 Family; C096127:ALDH2 protein, human; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; C510223:ALDH1A1 protein, human; D050697:Retinal Dehydrogenase; D005996:Nitroglycerin; D006152:Cyclic GMP