title: Metabolism of NAD(P)H by blood components. Relevance to bioreductively activated prodrugs in a targeted enzyme therapy system.
abstract: NADH was metabolized both by serum components and at the cell surface. The metabolism by serum was either oxidation to NAD+, or hydrolysis of the pyrophosphate to yield nicotinamide mononucleotide (reduced) (NMNH) and AMP. NMNH was further hydrolysed to yield nicotinamide riboside (reduced) (NRH), which was stable. NAD+ was hydrolysed (although at a slower rate than was NADH), but was also reduced to yield NADH. The reduction of NAD+ was catalysed by the enzyme serum L(+)lactate dehydrogenase (EC 1.1.1.27) and was dependent on the concentration of L(+)lactate in the serum. NADPH was hydrolysed in a similar manner to NADH but not oxidized by serum. NADH generated from NAD+ by serum derived from human, foetal calf and horse sources was capable of driving the bioreductive activation of CB 1954 by the enzyme DT diaphorase. Cell surfaces oxidized NADH to NAD+, but did not oxidize NADPH or NRH. These observations suggest that NAD(P)H would be unsuitable as a source of reducing equivalents for the bioreductive activation of prodrugs by a reductase enzyme in Antibody Directed Enzyme Prodrug Therapy (ADEPT). In contrast, NAD+ (which could act as a source of NADH) and NRH could avoid the shortcomings of NAD(P)H, and act as suitable cofactors for an enzyme in an ADEPT system.
authors.affiliation: Molecular Pharmacology Unit, Institute of Cancer Research, Surrey, U.K.
authors.forename: F
authors.initials: F
authors.lastname: Friedlos
authors.forename: R J
authors.initials: RJ
authors.lastname: Knox
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism; D001388:Aziridines / Q000378:metabolism; D001711:Biotransformation; D001769:Blood; D001777:Blood Coagulation; D002417:Cattle; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D006736:Horses; D006801:Humans; D006868:Hydrolysis; D007773:Lactates / Q000097:blood; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D009536:Niacinamide / Q000378:metabolism; D010084:Oxidation-Reduction; D011355:Prodrugs / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001388:Aziridines; D007773:Lactates; D011355:Prodrugs; D009243:NAD; D009536:Niacinamide; D009249:NADP; C100099:tretazicar; D008058:Dihydrolipoamide Dehydrogenase