Stimulation of the hexose monophosphate pathway in the human erythrocyte by Mn2+: evidence for a Mn2+-dependent NADPH peroxidase activity |
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| Authors: | A Bennun M A Needle V A DeBari |
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| Affiliation: | 1. Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States;2. Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, United States;1. Murdoch Childrens Research Institute, Royal Children''s Hospital, Flemington Rd, Parkville, Vic. 3052 Melbourne, Australia;2. Department of Paediatrics, University of Melbourne, Flemington Rd, Parkville, Vic. 3052 Melbourne, Australia |
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| Abstract: | In human RBC hemolysates, Mn2+ was found to stimulate the HMP as determined by the release of 14CO2 from [1-14C]glucose, providing activities of 125, 200, and 300% of basal at Mn2+ concentrations of 1, 10, and 100 mM, respectively. To explore the possibility that this stimulatory effect upon the HMP is a result of redox recycling of NADPH, RBC hemolysates were used to study NADPH oxidation. Mn2+, alone or in combination with a free radical-generating system, did not enhance the ability of hemolysates to oxidize NADPH. However, hemolysates + 10 mM H2O2 brought about a 10-fold increase in NADPH oxidation (0.51 +/- 0.05 nmole/min to 5.67 +/- 0.84 nmole/min) and the addition of 10 mM Mn2+ to this system increased the rate of oxidation to 34.10 +/- 2.97 nmole/min. Boiled hemolysates, either in the presence or absence of Mn2+, had some residual catalytic activity. |
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