Lymphocyte ecto-5'-nucleotidase deficiency in agammaglobulinemia.

Fresh peripheral blood lymphocytes from eight patients with congenital agammaglobulinemia demonstrate reduced ecto-5'-nucleotidase activity when compared to the mean activity of normal subjects and patients with other forms of immunoglobulin deficiency. A specific defect of ecto-5'-nucleotidase is further suggested by normal values for lymphocyte ecto-adenosinetriphosphatase and ecto-nonspecific phosphatase. The data provide evidence for an enzyme deficiency in this X-linked, B lymphocyte deficiency syndrome.

Effects of low-level lead exposure on pyrimidine 5'-nucleotidase and other erythrocyte enzymes. Possible role of pyrimidine 5'-nucleotidase in the pathogenesis of lead-induced anemia.

Similarities between lead-induced anemia and a new hereditary erythorenzymopathy involving pyrimidine-specific 5'-nucleotidase prompted studies of the effects of lead on this and other erythrocyte enzymes. In vitro incubations of normal mature erythrocytes demonstrated that significant inhibition of pyrimidine 5'-nucleotidase occurred in the presence of lead at concentrations that had minimal effects on many other erythrocyte enzymes assayed simultaneously. Similarly, subjects with chronic lead intoxication secondary to industrial exposure exhibited substantial and consistent impairment of erythrocyte pyrimidine-5'-nucleotidase activity. Results suggest that lead-induced deficiency of this enzyme in maturing erythroid elements could, if sufficiently severe, result in induction of basophilic stippling and premature erythrocyte hemolysis analogous to that encountered in the genetically induced enzyme-deficiency syndrome.

Lead poisoning. Further observations on erythrocyte pyrimidine-nucleotidase deficiency and intracellular accumulation of pyrimidine nucleotides.

Pyrimidine nucleotides, detectable in normal erythrocytes only in trace quantities if at all, were found to comprise 7-80% of the intracellular nucleotide pools in nine subjects with severe lead over-burden. Blood lead concentrations ranged from approximately equal to 200- to 400-microgram/dl packed cells, and the greatest accumulations of pyrimidine-containing nucleotides occurred in the two subjects with the highest blood lead levels. Most of the patients had mild or moderate anemia and moderate basophilic stippling evident in Wright's-stained peripheral smears. Pyrimidine nucleotidase activities were inhibited to 13-28% of the mean activity in normal control erythrocytes and even more so (5-15%) when compared to specimens with increased reticulocytes and young cells. Reticulocytosis was absent in two subjects and modest to moderate in the remainder, but erythrocyte assays revealed the substantial elevations in populations of young mean cell age. Inappropriately low reticulocyttial elevations in glucose-6-phosphate dehydrogenase expected in populations of young mean cell age. Inappropriately low reticulocyte responses may reflect hematopoietic suppressive effects of lead at a variety of metabolic loci.

Lead poisoning: association with hemolytic anemia, basophilic stippling, erythrocyte pyrimidine 5'-nucleotidase deficiency, and intraerythrocytic accumulation of pyrimidines.

Lead intoxication is accompanied by an acquired deficiency of erythrocyte pryimidine-specific, 5'-nucleotidase. Genetically determined deficiency of this enzyme is associated with chronic hemolysis, marked basophilic stippling of erythrocytes on stained blood films, and unique intraerythrocytic accumulations of pyrimidine-containing nucleotides. The present report documents that lead-induced deficiency when sufficiently severe gives rise to findings similar to the hereditary disorder. Whereas pyrimidine-containing nucleotides are virutally absent in the erythrocytes of normal and reticulocyte-rich blood, 12% of erythrocyte nucloetides in the blood of a patient with lead intoxication contained cytidine. Nucleotidase activity was about 25% that in normal erythrocytes and 15% or less of that expected in comparable reticulocyte-rich blood. The distribution of nucleotidase activity in patient erythrocytes is unknown, and much more severe deficiency could have been present in subsets of the cell populations analyzed. The findings indicate that the hemolytic anemia and increased basophilic stippling characteristic of certain cases of lead intoxication may share a common etiology with essentially identical features of the genetically determined disorder.

Pyrimidine nucleotides impair phosphoribosylpyrophosphate (PRPP) synthetase subunit aggregation by sequestering magnesium. A mechanism for the decreased PRPP synthetase activity in hereditary erythrocyte pyrimidine 5'-nucleotidase deficiency.

The activity of phosphoribosylpyrophosphate (PRPP) synthetase (ATP: D-ribose-5-phosphate pyrophosphotransferase, EC 2.7.6.1) is decreased in the erythrocyte in hereditary pyrimidine 5'-nucleotidase (P5N) deficiency. Given the increased pyrimidine nucleotide content of the P5N-deficient erythrocyte, we evaluated the effects of prototypic pyrimidine nucleotides on the activity of PRPP synthetase. In normal hemolysate a 1.0 mM combination of cytidine tri-, di- and monophosphate (CTP/CDP/CMP) inhibited PRPP synthetase activity and changed the ribose 5-phosphate (R5P) saturation curve from a hyperbola to a biphasic shape. Untreated crude hemolysate from P5N-deficient erythrocytes showed a biphasic R5P kinetic curve. Since the activity of PRPP synthetase is dependent on its state of subunit aggregation, we examined PRPP synthetase subunit aggregation using gel permeation chromatography. P5N-deficient erythrocytes had a decreased absolute amount of aggregated PRPP synthetase and almost a total loss of disaggregated PRPP synthetase. Using normal hemolysate, 1 mM CTP/CDP/CMP interfered with the ability of 1.0 mM ATP and 2.0 mM MgCl2 to promote PRPP synthetase subunit aggregation. Increasing the MgCl2 to 6.0 mM overcame the inhibitory effect of CTP/CDP/CMP. Thus, the decreased PRPP synthetase activity of the P5N-deficient erythrocyte is due, at least in part, to the ability of the accumulated pyrimidine nucleotides to sequester magnesium and to interfere with the subunit aggregation of PRPP synthetase.

Substrate specificity and pH sensitivity of deoxyribonucleotidase and pyrimidine nucleotidase activities in human hemolysates.

Residual 5'-nucleotidase activities in hemolysates from nine subjects with severe hereditary deficiency of pyrimidine nucleotidase (PyrNase) were compared to those in normal and reticulocyte-rich controls. Dephosphorylation rates of 12 potential ribo- and deoxyribomononucleotide substrates were measured as a function of pH. Data confirmed the existence of at least two isozymes of 5'-nucleotidase, PyrNase, and 2'-deoxy-5'-ribonucleotide phosphohydrolase (dNase) distinguishable by differences in maximal velocities, substrate preferences and restrictions, and pH optima. PyrNase was confirmed to be active principally with pyrimidine substrates (UMP = dCMP greater than CMP much greater than dTMP greater than dUMP) at a pH optimum of 7.5 +/- 0.1. dNase activity occurred with both purine and pyrimidine substrates and was maximal with deoxy analogs (dIMP much greater than dUMP greater than dGMP greater than dTMP = dAMP much greater than dCMP) at a pH optimum of 6.2, but slight cross-reactivity occurred with some nondeoxy substrates (IMP greater than GMP greater than UMP = XMP greater than CMP). PyrNase and dNase may be complementary systems that serve physiologically to clear the cytosol of RNA and DNA degradation products during maturation of erythroid elements by conversion of nucleotide monophosphates to diffusible nucleosides.

Pyrimidine metabolism in hereditary erythrocyte pyrimidine 5' nucleotidase deficiency.

A patient with hereditary erythrocyte pyrimidine 5' nucleotidase deficiency was studied to determine the mechanism of accumulation of erythrocyte pyrimidine nucleotides. Estimates of the rate of degradation of uridine nucleotides to diffusable products imply that the high levels found in these patients could not be sustained from the degradative pathways alone. Active synthesis of uridine nucleotides was found to occur in erythrocytes from both patient and control blood samples when either uridine or orotate was used as a substrate. The circulating levels of uridine in the blood are such that sufficient nucleotides to account for the high levels seen in these patients could accumulate in the erythrocytes from biosynthetic pathways alone, quite apart from the contribution from degradation of residual ribosomal RNA. This provides scope for new therapeutic approaches; treatment with allopurinol, however, was found to result in an increase, rather than a decrease, in erythrocyte pyrimidine nucleotides.

Metabolic basis for disorders of purine nucleotide degradation.

Purine nucleotide degradation refers to a regulated series of reactions by which human purine ribonucleotides and deoxyribonucleotides are degraded to uric acid in humans. Two major types of disorders occur in this pathway. A block of degradation occurs with syndromes involving immune deficiency, myopathy or renal calculi. Increased degradation of nucleotides occurs with syndromes characterized by hyperuricemia and gout, renal calculi, anemia or acute hypoxia. Management of disorders of purine nucleotide degradation is dependent upon modifying the specific molecular pathology underlying each disease state.

Purine enzymes and immune function.

The term immune function is taken to mean the process by which lymphocytes respond to an antigenic challenge. This response involves cell division and differentiation, which depend on purine nucleotides. The present state of knowledge relating events at the cell surface to the necessarily increased rate of purine de novo synthesis, and the modulation of purine nucleotide interconversions through the mediation of putative intracellular messengers, is reviewed. These physiological processes are related, where possible, to some genetic and pharmacologically induced perturbations of the systems involved.

Electrophoretic and kinetic studies of human erythrocytes deficient in pyrimidine 5'-nucleotidase.

A new variant of hereditary hemolytic anemia due to erythrocyte pyrimidine 5'-nucleotidase deficiency was found in Japan. Biochemical parameters such as the Michaelis constant, thermostability, electrophoresis and pH curve were studied. The variant showed a high Michaelis constant for cytidine 5'-monophosphate, no thermolability, slower electrophoretic mobility and abnormal optimum pH. The results strongly suggest that the mechanism of this enzyme deficiency is due to a structural gene mutation.

Electrophoretic and kinetic studies of a mutant red cell pyrimidine 5'-nucleotidase.

Human red cell pyrimidine 5'-nucleotidase (P5N) was studied by partial purification and condensation in a patient with an extremely low red cell P5N activity and chronic hemolytic anemia. The residual P5N in the red cell of the patient was characterized by an increased Michaelis constant for cytidine 5'-monophosphate, a marked shift of the pH optimum to the acidic side, normal electrophoretic mobility and normal heat stability. These data indicate that, in this patient, severe enzyme deficiency is caused by a structural gene mutation. This variant is clearly distinguished from a previously reported case and it is designated P5N Kagoshima.

Erythrocyte nucleotide pattern in two children in a Norwegian family with pyrimidine 5'-nucleotidase deficiency.

In the erythrocytes from two Norwegian children, a brother and a sister, with a hemolytic anemia due to pyrimidine 5'-nucleotidase deficiency, the pyrimidine and purine nucleotides have been investigated using HPLC with a strong anionic exchanger. The standard procedure was complemented with some additional elution systems which made it feasible to separate in the extract and to analyse, in addition to the conventional mono-, di- and triphosphates, UDP-glucose, UDP-N-acetylglucosamine, CDP-choline and CDP-ethanolamine. The two different purine nucleotides (A, G) and the two different pyrimidine nucleotides (U, C) exhibited normal ratios (energy charge ratios) between the conventional nucleotides. This would indicate that the erythrocytes have a sufficient energy production. It is suggested that the partly intravascular hemolysis might be due to disturbed synthesis of phospholipids.

Three families with hereditary hemolytic anemia and pyrimidine 5'-nucleotidase deficiency: electrophoretic and kinetic studies.

Three new variants of pyrimidine 5'-nucleotidase (P5N) found in Japan were studied. They are characterized by slow electrophoretic mobility and a high Michaelis constant for cytidine 5'-monophosphate as has been described in previously reported cases, but are unique with respect to the thermostability test and in pH optima. P5N Kumamoto was thermostable and showed a markedly basic shift in the pH optimum. P5N Nagano was thermolabile and had a normal pH optimum. P5N Kurume was thermostable and showed a basic shift in the pH optimum. These data suggest that these variants have structural gene mutations and that they are clearly distinguished from previously reported cases.

Red cell pyrimidine 5' nucleotidase deficiency: determination of nucleotidase activity and nucleotide content using HPLC.

The hereditary deficiency of erythrocyte pyrimidine 5' nucleotidase has been investigated using an HPLC anion-exchange procedure designed to measure both red cell nucleotide content and enzymic activity. Red cell nucleotide profiles were determined using a low pH phosphate buffer salt-gradient system in 20 min, whereas a low pH buffer alone permitted the determination of enzymic activity with each of six different nucleotide substrates in less than 4 min. Both the red cell nucleotide profiles and the enzymic activity of haemolysates from two affected brothers and their children agreed well with previously published values. This unified approach should prove useful for detailed studies of deficiencies involving isoenzymes of pyrimidine nucleotidase.

ATP, ADP and AMP in plasma from peripheral venous blood.

ATP, ADP and AMP in concentrations at least 1 mumol/l have been found by high pressure liquid chromatography (HPLC) in plasma from peripheral venous blood. Total adenine nucleotide concentrations of about 15-20 mumol/l can be found in some conventional clinical samples of blood using EDTA as an anticoagulant. EDTA prevented adenine nucleotide conversion to inosine in plasma. In order to estimate concentrations in vivo, the contribution derived from the cell breakage inherent even in careful venous blood sampling has been estimated by extrapolation to zero 'haemoglobin' concentration in plasma and minimum values in samples of small volume. Available results appear to be consistent with the release of small amounts of ATP in or near the peripheral circulation at the time of venepuncture. In CSF, ATP, ADP and AMP concentrations were less than 0.05 mumol/l suggesting that membrane activity in the central nervous system is not associated with non-specific leakage. The high Km variant of lymphocyte ecto-5'-nucleotidase was not associated with a significantly higher concentration of its substrate AMP in plasma. However, this enzyme may function on the lymphocyte in the thymus and spleen.

Study of a case with severe red-cell pyrimidine 5'-nucleotidase deficiency.

A deficiency of erythrocyte pyrimidine 5'-nucleotidase was found in a 23-year-old male suffering from severe congenital hemolytic disease. Results from exhaustive metabolic exploration are given and compared with reticulocyte-rich blood from subjects with auto-immune hemolytic disease. Evidence is given that the 20% apparent P5N residual activity corresponds to a non-specific acid phosphatase.

Hemolytic anemia in hereditary pyrimidine 5'-nucleotidase deficiency. II. Effect of pyrimidine nucleotides and their derivatives on glycolytic and pentose phosphate shunt enzyme activity.

We evaluated the glycolytic intermediate concentrations from the erythrocytes of a patient with hereditary pyrimidine 5'-nucleotidase (P5'N) deficiency. Conclusive evidence for a metabolic block was not found. We evaluated the effects of the pyrimidine (cytidine and uridine) tri- and diphosphate nucleotides (CTP, CDP, UTP, UDP) and the choline and ethanolamine derivatives of CDP (CDP-choline, CDP-ethanolamine) on the activities of key enzymes of the Embden-Meyerhof pathway. CTP and UTP inhibited fructose-6-phosphate competitively for phosphofructokinase and phosphoenolpyruvate competitively for pyruvate kinase. In both cases, the Ki of the pyrimidine nucleotide and Km of the glycolytic substrate were above their intraerythrocytic concentrations. CTP was a competitive inhibitor of ADP for pyruvate kinase with a Ki near its intraerythrocytic concentration. CDP-choline and CDP-ethanolamine had no effect on the activities of Embden-Meyerhof or pentose phosphate shunt enzymes. Thus, the nature of the hemolytic anemia in hereditary P5'N deficiency remains enigmatic.

Erythrocyte enzyme disorders in children.

Erythrocyte metabolic abnormalities should be considered as a possible cause of hemolysis when there is no evidence of an immune-mediated hemolytic anemia, no consumptive red blood cell disorder, no morophologic or laboratory data to suggest a problem of the red cell membrane, and no evidence of a quantitative or qualitative defect in hemoglobin synthesis. Glucose-6-phosphate dehydrogenase deficiency is clearly the most common enzyme deficiency causing clinical problems.

Clinical consequences of enzyme deficiencies in the erythrocyte.

The anucleate mature erythrocyte also lacks ribosomes and mitochondria and thus cannot synthesize enzymes or derive energy from the Krebs citric acid cycle. Nevertheless, the red blood cell is metabolically active and contains numerous residual enzymes and their products which are essential for its survival and normal functioning. Enzyme deficiencies in the Embden-Myerhoff glycolytic pathway can result in nonspherocytic hemolytic anemia (NSHA), and some are also associated with neuromuscular or neurologic disorders. Glucose-6-phosphate dehydrogenase deficiency in the hexose monophosphate shunt also results in hemolytic anemia, especially following exposure to various drugs. Defects in glutathione synthesis and pyrimidine 5'-nucleotidase deficiency also cause NSHA, as does increased adenosine deaminase activity. Gluthathione synthetase deficiency which is not limited to the red cell also presents as oxoprolinuria with neurologic signs. All red cell enzyme defects appear as single gene errors, in most cases recessive in inheritance, either autosomal of X-linked.

[Glucose-6-phosphate dehydrogenase deficiency and other erythrocyte enzyme abnormalities]. / Glukose-6-Phosphatdehydrogenasemangel und andere Enzymanomalien in Erythrozyten.

Normal values of glucose-6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), glutathione reductase (GR), glucosephosphate isomerase (GPI), pyruvate kinase (PK) and pyrimidine 5'-nucleotidase (P5N) have been determined in normocytes, reticulocytes, newborn cord erythrocytes, and leucocytes. Metabolic and clinical aspects of G6PD and the classification of its genetic variants are reviewed. Enzyme determinations and their variation in drug-induced haemolysis are critically presented. Extensive tables are published listing the drugs and compounds that can cause haemolysis in G6PD-deficient patients, as well as those preparations which may, probably, be administered safely. Clinical and biochemical data in patients with the inherited enzyme defects GR, GPI, PK, and P5N, as well as acquired deficiency of the last-mentioned in chronic lead intoxication, are reviewed in the light of our personal experience in this field.