Recycling enzymatic assay of NAD—Interference by an activator in human erythrocytes

Nicotinamide nucleotides play an important role in cellular metabolism. Sander et al. (1) have described a procedure for the extraction of pyridine nucleotides from erythrocytes which circumvents most of the difficulties reported by others (2–4). For NAD assay simple recycling methods involving a single enzyme were employed by some authors (5–8), but the NAD extraction procedures adopted by them were essentially similar to the earlier methods. In the present study, an attempt was made to develop a simplified procedure for NAD estimation in human erythrocytes based on the existing improved methods of NAD extraction (1) and assay (6,7,9). During the experimentation, it became apparent that the erythrocyte extracts contained an interfering substance which accelerated the NAD cycling rate in the assay resulting in overestimation of the NAD content.