Preparation and Coenzymic Activity of Soluble Polyethyleneimine‐Bound NADP + Derivatives

Alkylation at N‐1 of the NADP + adenine ring with 3,4‐epoxybutanoic acid gave 1‐(2‐hydroxy‐3‐carboxypropyl)‐NADP + . Enzymic reduction of the latter, followed by alkaline Dimroth rearrangement and enzymic reoxidation, gave N 6 ‐(2‐hydroxy‐3‐carboxypropyl)‐NADP + . On the other hand, bromination at C‐8 of the NADP + adenine ring, followed by reaction with the disodium salt of 3‐mercaptopropionic acid, gave 8‐(2‐carboxyethylthio)‐NADP + . Carbodiimide coupling of the three carboxylic NADP + derivatives to polyethyleneimine afforded the corresponding macromolecular NADP + analogues. The carboxylic and the polyethyleneimine derivatives synthesized have been shown to be co‐enzymically active with yeast glucose‐6‐phosphate dehydrogenase, liver glutamate dehydrogenase and yeast aldehyde dehydrogenase. The degree of efficiency relative to NADP + with the three enzymes ranged from 17% to 100% for the carboxylic derivatives and from 1% to 36% for the polyethyleneimine analogues. On comparing the efficiencies with the three enzymes of the N‐1 derivatives to the one of the corresponding N 6 and C‐8 analogues, the order of activity was N‐1 > N 6 > C‐8, except in the case of the carboxylic compounds with glutamate dehydrogenase, where this order was inverted. None of these modified cofactors were active with pig heart isocitrate dehydrogenase.