Preparation of stereospecific tritium-labeled reduced nicotinamide adenine dinucleotide phosphate

Synthesis of R and S tritiated reduced beta-nicotinamide adenine dinucleotide 2' phosphate

Nicotinamides are ubiquitous cofactors used by many biological systems as redox agents. Stereospecifically labeled cofactors are useful in many studies of nicotinamide-dependent enzymes. Enzyme-directed synthesis of these cofactors is rather common but their stability imposes significant challenges on yield, purity, and preservation. This paper presents the stereospecific synthesis of reduced R- and S-[4-3H] beta-nicotinamide adenine dinucleotide 2' phosphate (NADPH). The method of Valera et al. [Biochem. Biophys. Res. Commun. 148 (1987) 515] was modified to a synthetic procedure that produces both isotopic diastereomers within 2h with an improved yield of 75-90% after purification and lyophilization. In the synthesis, [4-3H]NADP+ was generated as an intermediate (which can be isolated if desired). The specific radioactivities reported here are 2.7 and 1.1 Ci/mmol for the S and R diastereomers, respectively. Specific radioactivities ranging from carrier-free to trace labeling can be achieved with a minor change to the procedure.

Enzymatic synthesis of [4R-2H]NAD (P)H and [4S-2H]NAD(P)H and determination of the stereospecificity of 7 alpha- and 12 alpha hydroxysteroid dehydrogenase

The stereospecifically labeled coenzymes [4R-2H]NADH, [4R-2H]NADPH and [4S-2H]NAD(P)H were synthesized enzymatically in high yield and high isotopic purity (greater than or equal to 95%) with 2HCOO2H/formate dehydrogenase, (CH3)2C2HOH/alchol dehydrogenase from Thermoanaerobium brockii and [1-2H]glucose/glucose dehydrogenase, respectively. This set of deuterated coenzymes was used to determine the stereospecificity of the previously unstudied 7 alpha-hydroxysteroid dehydrogenase from Escherichia coli (NAD-dependent) and 12 alpha-hydroxysteroid dehydrogenase from Clostridium group P (NADP-dependent). H-NMR and EI-MS of the nicotinamide moiety after enzymatic oxidation of deuterated NAD(P)H with dehydrocholic acid as substrate showed that both dehydrogenases are B-sterospecific.

Synthesis of 4R- and 4S-tritium labeled NADPH for the determination of the coenzyme stereospecificity of NADPH: protochlorophyllide oxidoreductase

A rapid and easy method for the production of both the 4R and 4S tritium labeled isomers of either NADH or NADPH has been developed. The method requires the use of only a single labeled compound (D-[1(-3)H] glucose), and two enzymes (glucose dehydrogenase from Bacillus sp. and alcohol dehydrogenase from Thermoanaerobium brockii) which are specific for the pro S and pro R hydrogens, respectively, of either NADH or NADPH. The 4R and 4S tritium labeled isomers of NADPH have been used to determine that NADPH:protochlorophyllide oxidoreductase from etiolated wheat was specific for the pro S hydrogen of NADPH.