Dual coenzyme activities of high-Km aldehyde dehydrogenase from rat liver mitochondria.
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.
Tsai
C S
CS
Ottawa-Carleton Chemistry Institute, Carleton University, Ont., Canada.
Senior
D J
DJ
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
D003067:Coenzymes; D007527:Isoenzymes; D009243:NAD; D009249:NADP; D000444:Aldehyde Dehydrogenase; D000079:Acetaldehyde