[Method for testing niacin bound activities in man].

In order to value the availability of niacin in man, it has been more suitable to test erythrocyte nicotinate-phosphoribosyltransferase and nicotinamide-phosphoribosyltransferase activities. These enzymes catalyze the production of Des-NMN and NMN from free bases. The radioactive compounds, produced from [14C] NAc and [14C] NAm, are isolated by a gel chromatography and counted in liquid scintillation. It has been observed that nicotinamide-phoshoribosyltransferase is scarcely active in human erythrocytes, while the nicotinate-phosphoribosyltransferase gives a good indication of niacin availability.