28] Coenzyme activity of NAD+ bound to polymer supports through the adenine moiety

Abstract

This chapter discusses the coenzyme activity of nicotinamide adenine dinucleotide (NAD+) bound to polymer supports through the adenine moiety. Binding of NAD+ to high molecular-weight, supports for the preparation of affinity gels and has sometimes been performed by methods that are not exactly defined in regard to the substitution site of the coenzyme. Even in cases of defined binding, the coenzyme activity of NAD+ gels has not been determined. These gels are quite useful for affinity chromatography, because affinity binding is still possible at other loci within the active site. NAD+-specific dehydrogenases are retained, by affinity gels, bearing immobilized adenosine monophosphate (AMP). NAD+ bound to high molecular-weight supports can only be reduced by enzymes, if the formation of a complete enzyme-coenzyme complex is possible. Ideally the binding of the coenzyme to the polymer should not greatly affect its biological activity. Suitable methods are, therefore, limited to substitutions at one of the positions mentioned above. In this chapter, syntheses and properties of N6- and C8-substituted NAD+ analogs are discussed. Binding of NAD+ to polymers through the N6 and the C8 position and properties of the resulting derivatives are also described in the chapter.