Oxidation of Reduced Triphosphopyridine Nucleotide by Guinea Pig Polymorphonuclear Leucocytes

Abstract

THE phagocytic process in guinea pig polymorphonuclear leucocytes (PMN) is accompanied by increases in the rates of oxygen consumption, of glucose oxidation by the hexosemonophosphate shunt and of formate oxidation to carbon dioxide^1–3. The availability of triphosphopyridine nucleotido (NADP) appears to regulate the rate of glucose oxidation by the shunt in leucocytes^3,4. Attempts have been made to correlate the stimulated activity of the hexosemonophosphate shunt in phagocytizing leucocytes with increased NADPH oxidation. The evidence indicates that NADPH oxidation in phagocytizing leucocytes is not accomplished by the classical route of hydrogen transport by way of cytochrome reductase and cytochrome c (ref. 1) nor by means of an NADP-linked lactate dehydrogenase². Iyer, Islam and Quastal^2,3 obtained results showing that PMN possess an enzyme system capable of oxidizing NADPH and NADH by a reaction involving the formation of hydrogen peroxide. The enzyme, however, is much more active towards NADPH than towards NADH and its activity is strongly enhanced by manganese ions³. Rechcigl and Evans⁵ have suggested that a hydrogen-peroxide-destroying system, such as myeloperoxidase, which is found in high concentrations in leucocytes⁶ may be important in protecting the cell from toxic effects of hydrogen peroxide. Results described here show that the oxidation of reduced triphosphopyridine nucleotide in PMN may be accomplished by a reaction involving peroxidase.