³¹P NMR study of erythrocytes from a patient with hereditary pyrimidine-5'-nucleotidase deficiency

Authors

M. S. Swanson, University of Nebraska Medical Center
C. R. Angle, University of Nebraska Medical Center
S. J. Stohs, University of Nebraska Medical Center
S. T. Wu, University of Nebraska Medical Center
J. M. Salhany, University of Nebraska Medical Center
R. S. Elliot, University of Nebraska Medical Center
R. S. Markin, University of Nebraska Medical CenterFollow

Date of this Version

1983

Comments

Published in Proc. Natl. Acad. Sci. USA (1983) vol. 80, 169-172

Abstract

The composition of phosphate metabolites and the intracellular pH in erythrocytes from a patient with hereditary pyrimidine-5'-nucleotidase deficiency were examined using ³¹P NMR spectroscopy. Several resonances were identified in spectra from intact cells and from extracts. The 2,3-bisphosphoglycerate line intensities were normal but the NTP resonances were about twice normal due to the presence of millimolar quantities of pyrimidine phosphates. Several intense resonances were also observed in the diphosphodiester region of the spectrum. One compound contributing to these lines has been identified as cytidine diphosphocholine. The resonances of NTPs were in a position indicating that the additional triphosphates were also bound by Mg²⁺. Direct measurement shows that there is a nearly proportional increase in total cell Mg²⁺ in the patient's cells, in agreement with the interpretation of the spectra. The intracellular pH was about 0.2 unit lower in the patient's erythrocytes. This lower pH is due to the elevation in intracellular fixed negative charges and the shift in permeable anions consequent to the Donnan equilibrium. We suggest that the lower intracellular pH may explain the lower oxygen affinity of these cells in the presence of otherwise normal 2,3-bisphosphoglycerate levels and the increased Mg²⁺ triphosphates level, because the Mg²⁺ form of NTPs is known not to alter the oxygen affinity of hemoglobin under physiologic conditions. Furthermore, the lower intracellular pH can also explain the abnormalities in glycolytic intermediates observed for these cells.