title: Dual coenzyme activities of high-Km aldehyde dehydrogenase from rat liver mitochondria.
abstract: Various kinetic approaches were carried out to investigate kinetic attributes for the dual coenzyme activities of mitochondrial aldehyde dehydrogenase from rat liver. The enzyme catalyses NAD(+)- and NADP(+)-dependent oxidations of ethanal by an ordered bi-bi mechanism with NAD(P)+ as the first reactant bound and NAD(P)H as the last product released. The two coenzymes presumably interact with the kinetically identical site. NAD+ forms the dynamic binary complex with the enzyme, while the enzyme-NAD(P)H complex formation is associated with conformation change(s). A stopped-flow burst of NAD(P)H formation, followed by a slower steady-state turnover, suggests that either the deacylation or the release of NAD(P)H is rate limiting. Although NADP+ is reduced by a faster burst rate, NAD+ is slightly favored as the coenzyme by virtue of its marginally faster turnover rate.
authors.affiliation: Ottawa-Carleton Chemistry Institute, Carleton University, Ont., Canada.
authors.forename: C S
authors.initials: CS
authors.lastname: Tsai
authors.forename: D J
authors.initials: DJ
authors.lastname: Senior
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D000818:Animals; D003067:Coenzymes / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008930:Mitochondria, Liver / Q000201:enzymology*; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003067:Coenzymes; D007527:Isoenzymes; D009243:NAD; D009249:NADP; D000444:Aldehyde Dehydrogenase; D000079:Acetaldehyde