A micellar model for investigating the chemical nature of hydrogen transfer in NAD(P)H-dependent enzymatic reactions.
Aqueous micelles of Triton X-100 were shown to catalyse the redox reaction between NADH and 2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazolium chloride (INT) at the neutral pH. The transfer of reducing equivalents between the reactants in the micellar system appeared to be direct and quantitative. N-tert-butylphenyl-alpha-nitrone, a lipophilic free-radical scavenger which can enter micelles, and superoxide dismutase did not alter the stoichiometry of the reaction. The oxidation product of NADH was found to be 100% enzymatically active. The IR spectrum of INT-formazan (i.e., the product of INT reduction) showed an absorbance at 3,100-3,700 cm- due to NH-stretching. The presence of NH proton, confirmed further by IH-NMR, together with the above observations suggests that INT, as part of the over-all redox process, abstracts a C(4) hydrogen of the dihydropyridine nucleus of NADH with a simultaneous cleavage at N(2-3) position of its 1,2,3,4-tetrazole ring system and that the redox events are confined to a microenvironment as in the case of NAD(P)H-dependent enzymatic reactions.
Rao
U M
UM
Department of Medicine, The Nizam's Institute of Medical Sciences, Hyderabad, India.
D003102:Colloids; D003902:Detergents; D006859:Hydrogen; D007700:Kinetics; D008823:Micelles; D008962:Models, Theoretical; D009243:NAD / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D017830:Octoxynol; D010084:Oxidation-Reduction; D011092:Polyethylene Glycols
D003102:Colloids; D003902:Detergents; D008823:Micelles; D009243:NAD; D011092:Polyethylene Glycols; D009249:NADP; D006859:Hydrogen; D017830:Octoxynol; D009247:NADH, NADPH Oxidoreductases