[Pyridine metabolism of the human erythrocyte]

Pyridine nucleotides are required for human erythrocyte survival, for their role in both glycolysis and pentose phosphate pathway. Human red blood cells have been used for the study of some pyridine nucleotide cycle reactions, but the whole sequence in the erythrocyte has not yet been completely determined. In the present work, pyridine coenzyme synthesis interrelationships and degradation have been revised, both in general and regarding to human erythrocytes. These cells are lacking the de novo pathway, and utilize exogenous free bases, especially nicotinic acid, as NAD precursors. Nicotinamide utilization is discussed in view of its role in the salvage pathway. Available data on enzyme kinetic and regulation characteristics are reviewed.