Characterization of NAD-glycohydrolase in rat lymphoid organs.

Rat thymus and thymocytes possess an NAD-glycohydrolase activity lower than spleen and spleen lymphocytes. In all cases, the highest activity (50%) is bound to the nuclei, while that in the soluble fraction is higher (in percent) in the lymphocytes than in the whole organ. Considering that thymus and thymocytes are characterized by a soluble NAD-ase activity higher than in spleen and in spleen lymphocytes, and that lymphocytes in general have a greater soluble than microsomal activity, we interpret these findings are evidence that the soluble NAD-ase is due essentially to T lymphocytes, of which it represents a typical feature.

[Method for testing niacin bound activities in man]. / Messa a punto di un metodo per la rivelazione nell'uomo di attivita' legate alla niacina.

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.