Familial hypogammaglobulinemia with variable serum immunoglobulins. Concordance with lymphocyte ecto-5'-nucleotidase deficiency

Four male subjects from two generations of a black family were found to have variable expression of hypogammaglobulinemia (IgG, IgM, and IgA deficiency in two, IgA deficiency in one, and IgM and IgA deficiency in another) and also to be moderately deficient in the lymphocyte plasma membrane enzyme, 5'-nucleotidase. The inheritance pattern of the immune abnormality is compatible with X linkage. The affected patients had normal numbers of complement receptor-bearing lymphocytes, variably depressed proportions of IgM- and IgD-bearing lymphocytes, and impaired ability to synthesize antibody after specific antigenic stimulation. In this family, the 5'-nucleotidase deficiency and the pattern of inheritance suggest that the different types of hypogammaglobulinemia may represent a variable expression of a common underlying genetic abnormality.

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.

Limited value of uric acid to creatinine ratios in estimating uric acid excretion

The value of the uric acid to creatinine ratio and the uric acid to creatinine clearance ratio in predicting 24-hour urinary uric acid excretion was assessed in 49 patients with normal enzyme activity and 22 patients with purine enzyme deficiencies. A 24-hour urinary uric acid to creatinine ratio greater than 0.75 was found in six of nine patients with a partial deficiency of hypoxanthine-guanine phosphoribosyltransferase and in all patients with Lesch-Nyhan syndrome. A ratio of less than 0.10 suggested xanthinuria or severe purine nucleoside phosphorylase deficiency. Neither ratio calculated from 2-hour timed collections of the 24-hour specimen showed a high correlation with 24-hour urine uric acid excretion in patients with normal enzyme activity, perhaps because of a diurnal variation in urinary uric acid excretion. The spot-urine uric acid to creatinine ratio does not accurately predict the 24-hour urine uric acid excretion in patients with normal enzyme activity.

Decreased S-adenosylhomocysteine hydrolase in inborn errors of purine metabolism

A deficiency of erythrocyte S-adenosylhomocysteine hydrolase has been confirmed in three patients with adenosine deaminase deficiency. In addition, erythrocyte S-adenosylhomocysteine hydrolase activity was decreased by 85% in three patients with purine nucleoside phosphorylase deficiency and by 57% in 15 patients with hypoxanthine-guanine phosphoribosyltransferase deficiency. Cultured diploid fibroblasts from these patients were normal. Besides deoxyadenosin, no compound known to accumulate in these disorders caused S-adenosylhomocysteine hydrolase inactivation. S-adenosylhomocysteine hydrolase had a normal half-life in the erythrocytes from two patients with Lesch-Nyhan syndrome. A secondary deficiency of S-adenosylhomocysteine hydrolase may accompany a number of inborn errors of purine metabolism. Whether this enzyme deficiency contributes to the molecular pathology of these diseases is not known.

Human placental adenosine kinase. Kinetic mechanism and inhibition

The kinetic properties of human placental adenosine kinase, purified 3600-fold, were studied. The reaction velocity had an absolute requirement for magnesium and varied with the pH. Maximal activity was observed at pH 6.5 with a Mg2+:ATP ranging from 1:1 to 2:1. High concentrations of Mg2+ or free ATP were inhibitory. Double reciprocal plots of initial velocity studies yielded intersecting lines for both adenosine and MgATP2-. The Michaelis constant was 0.4 micro M for adenosine and 75 micro M for MgATP2-. Inhibition by adenosine was observed at concentrations greater than 2.5 micro M. AMP was a competitive inhibitor with respect to adenosine and a noncompetitive inhibitor with respect to ATP. ADP was a noncompetitive inhibitor with respect to adenosine and ATP. Hyperbolic inhibition was observed during noncompetitive inhibition of adenosine kinase by AMP and ADP. Other purine and pyrimidine nucleoside mono-, di-, and triphosphates were poor inhibitors in general. S-Adenosylhomocysteine and 2'-deoxyadenosine inhibited adenosine kinase. The data suggest that (a) MgATP2- is the true substrate of adenosine kinase, and both pH and [Mg2+] may regulate its activity; (b) the kinetic mechanisms of adenosine kinase is Ordered Bi Bi; and (c) adenosine kinase may be regulated by the concentrations of its products, AMP and ADP, but is relatively insensitive to other purine and pyrimidine nucleotides.

Familial hyperuricemia and renal disease

Information on a familial syndrome of hyperuricemia and renal disease with or without gout was obtained on 33 of 41 blood relatives: Nine had renal disease; abnormalities of the urinary sediments were minimal; serum uric acid levels were elevated in seven and were not measured in two. Hyperuricemia was noted in three additional family members without evidence of renal disease. Goulty arthritis (three patients) did not precede renal disease. One individual had hyperuricosuria. The following erythrocyte purine enzyme levels were normal: adenine phosphoribosyltransferase, hypoxanthine-guanine phosphoribosyltransferase, phosphoribosylpyrophosphate, synthetase, adenosine deaminiase, and purine nucleoside phosphorylase. Renal biopsy specimens showed focal global and segmental sclerosis of glomeruli, occasional hypercellularity, foci of atrophic tubules, chronic interstitial inflammation, and folding and wrinkling of glomerular basement membrane without electron-dense deposits. There were no immunofluorescent abnormalities.

Altered purine and pyrimidine metabolism in erythrocytes with purine nucleoside phosphorylase deficiency

Purine and pyrimidine metabolism was compared in erythrocytes from three patients from two families with purine nucleoside phosphorylase deficiency and T-cell immunodeficiency, one heterozygote subject for this enzyme deficiency, one patient with a complete deficiency of hypoxanthine-guanine phosphoribosyltransferase, and two normal subjects. The erythrocytes from the heterozygote subject were indistinguishable from the normal erythrocytes. The purine nucleoside phosphorylase deficient erythrocytes had a block in the conversion of inosine to hypoxanthine. The erythrocytes with 0.07% of normal purine nucleoside phosphorylase activity resembled erythrocytes with hypoxanthine-guanine phosphoribosyltransferase deficiency by having an elevated intracellular concentration of PP-ribose-P, increased synthesis of PP-ribose-P, and an elevated rate of carbon dioxide release from orotic acid during its conversion to UMP. Two hypotheses to account for the associated immunodeficiency--that the enzyme deficiency leads to a block of PP-ribose-P synthesis or inhibition of pyrimidine synthesis--could not be supported by observations in erythrocytes from both enzyme-deficient families.

Purine metabolism during strenuous muscular exercise in man

This study was designed to examine the influence of exercise on purine metabolism in man. In 15 men, the plasma uric acid concentration increased from 6.9 to 8.5 mg/dl following a 5000-m race and from 6.2 to 7.9 mg/dl in 11 men following a 42-km marathon. During a progressive exercise test on a cycle ergometer, the plasma uric acid ocnentration did not change significantly in 11 subjects. However, the plasma oxypurines increased from 19 micrM at rest to 50 microM at exhaustion and the urinary excretion of oxypurines increased from 140 to 400 mumol/g creatinine. Intracellular ATP decreased from 5.17 to 2.91 mumol/g and ADP and AMP increased from 0.85 to 1.29 and from 0.12 to 0.15 mumol/g wet weight, respectively. These observations suggest that there is an accelerated degradation of purine nucleotides to the precursors of uric acid in skeletal muscle during vigorous exercise.

Histochemical evaluation of lymphocytes in hypogammaglobulinemia. Decreased number of 5'-nucleotidase-positive cells

With the use of a histochemical technique, 5'-nucleotidase activity was examined in peripheral blood lymphocytes from patients with primary hypogammaglobulinemia. Our current study demonstrates that the decrease in 5'-nucleotidase activity in congenital agammaglobulinemia, previously demonstrated by a radiochemical assay, is associated with a reduction in the number of cells containing 5'-nucleotidase rather than with a decrease of the enzyme activity per cell. Both sheep erythrocyte rosette-forming and nonrosette-forming PBMs have reduced percentages of 5'-nucleotidase-containing cells in subjects with the enzyme deficiency. The reduced percentage of 5'-nucleotidase-containing mononuclear cells in patients with congenital agammaglobulinemia was evident in both monocyte-contaminated and monocyte-depleted cell preparations.

Hypoxanthine salvage in man: its importance in urate overproduction in the Lesch-Nyhan syndrome

1. A daily urinary excretion of 0.8 percent of the administered radioactivity results from the turnover of the labeled adenine nucleotide pool. 2. A 4-fold increase of urinary radioactivity excretion occurs in patients with the Lesch-Nyhan syndrome and support the role of impaired hypoxanthine salvage in the purine overexcretion associated with HGPRT deficiency. 3. Our data do not support the possibility that the increased radioactivity excretion in the HGPRT deficient subjects results from an elevated rate of adenine nucleotide degradation.

Human placental adenosine kinase: purification and characterization

Human placental adenosine kinase has thus been purified 3600-fold and characterized with respect to molecular weight, substrate specificity, divalent cation requirements, pH optimum, isoelectric pH, and kinetic properties. These data contribute to the information currently available about the regulation of adenosine metabolism, information critical for an understanding of the biological properties of adenosine.

Distribution of 5'-nucleotidase in human lymphoid tissues

Low activity of 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) in T lymphoblasts may explain the marked sensitivity of this cell to deoxynucleotide accumulation when compared to B lymphoblasts. The relevance of such observations with cultured cells to the normal immune system requires the demonstration of similar differences in the 5'-nucleotidase activity of normal human lymphocyte subpopulations. Sheep erythrocyte (E) rosette-forming cells from normal thymus, tonsil, and peripheral mononuclear cells have 5'-nucleotidase activities of 1.7, 11.3, and 21.2 nmol/hr per 10(6) cells. Non-E-rosette forming cells from the peripheral blood or tonsil have 5'-nucleotidase activity comparable to the higher levels found in the peripheral E-RFC. Increased levels of 5'-nucleotidase activity may be a marker for post-thymic T lymphocytes. T lymphoblasts have 5'-nucleotidase activity similar to values demonstrated for E-RFC in thymus, whereas cultured B lymphoblasts have 5'-nucleotidase activity 15 times greater than that of T lymphoblasts. On the basis of these observations, the 5'-nucleotidase deficiency in congenital agammaglobulinemia has been reevaluated. In these patients the data indicate that peripheral E-rosette forming cells have the enzyme deficiency, demonstrating an abnormality of T lymphocytes in this disorder of immunoglobulin production.

Cellular immune deficiency with autoimmune hemolytic anemia in purine nucleoside phosphorylase deficiency

Immunologic and metabolic abnormalities were studied in a five year old boy with 0.07 per cent of normal erythrocyte purine nucleoside phosphorylase activity. The clinical course is characterized by severe autoimmune hemolytic anemia, a transient neurologic disorder with tremor and ataxia, and minor infectious illnesses. There is severe lymphopenia with decreased absolute numbers of T and B lymphocytes. Mitogen-stimulated blastogenesis is reduced, but response to allogeneic lymphocytes is normal. A monoclonal IgG protein is present. There is hypouricemia, elevated plasma inosine level, hypouricosuria and an increase in the urinary concentration of inosine and guanosine. The pattern of heterozygote distribution in the patient's family is compatible with an autosomal recessive trait in which heterozygotes are identifiable. In addition, the unusual laboratory and clinical manifestations of this patient illustrate the heterogeneity of the clinical syndrome associated with purine nucleoside phosphorylase deficiency.

Deoxyadenosine inhibits DNA synthesis in cultured human fibroblasts

The rate of DNA synthesis in cultured diploid fibroblasts, nonmalignant human cells, is decreased by 50 microM 2'-deoxyadenosine when adenosine deaminase is inhibited and 2'-deoxyadenosine is phosphorylated to dATP. No inhibiton of DNA synthesis occurs with 100 microM adenosine under identical conditions or with 50 microM deoxyadenosine when adenosine deaminase is not blocked. Inhibition of DNA synthesis may be an important link between adenosine deaminase deficiency and severe combined immunodeficiency if the tissue culture model is relevant to lymphocyte function in man.

Biochemical basis for differential deoxyadenosine toxicity to T and B lymphoblasts: role for 5'-nucleotidase

Deoxyadenosine metabolism was investigated in cultured human cells to elucidate the biochemical basis for the sensitivity of T lymphoblasts and the resistance of B lymphoblasts to deoxyadenosine toxicity. T lymphoblasts have a 20-to 45-fold greater capacity to synthesize deoxyadenosine nucleotides than B lymphoblasts at deoxyadenosine concentrations of 50--300 micron. During the synthesis of dATP, T lymphoblasts accumulate large quantities of dADP, whereas B lymphoblasts do not accumulate dADP. Enzymes affecting deoxyadenosine nucleotide synthesis were assayed in these cells. No substantial differences were evident in activities of deoxyadenosine kinase (ATP: deoxyadenosine 5'-phosphotransferase, EC 2.7.1.76) or deoxyadenylate kinase [ATP:(d)AMP phosphotransferase, EC 2.7.4.11]. The activity of 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) was increased 44-fold for AMP and 7-fold for dAMP in B lymphoblasts. A model for the regulation of deoxyadenosine nucleotide synthesis by 5'-nucleotidase activity is proposed on the basis of the observations.

Purine nucleoside phosphorylase deficiency: biochemical properties and heterogeneity in two families

The biochemical features of two families with purine nucleoside phosphorylase deficiency are compared. Laboratory studies and an evaluation of kinetic and physical properties of erythrocyte purine nucleoside phosphorylase give evidence that a) the degree of abnormality in uric acid and nucleoside concentrations in plasma and urine reflect the severity of the enzymatic deficiency and b) structural alterations of the mutant enzymes result from structural gene mutations and demonstrate genetic heterogeneity in the disease purine nucleoside phosphorylase deficiency.