Further data on the adenosine deaminase (ADA) polymprphism and a report of a new phenotype

Development of a Simple Assay Method for Adenosine Deaminase via Enzymatic Formation of an Inosine-Tb3+ Complex

Adenosine deaminase (ADA), which catalyzes the irreversible deamination of adenosine to inosine, is related to various human diseases such as tuberculous peritonitis and leukemia. Therefore, the method used to detect ADA activity and screen the effectiveness of various inhibitor candidates has important implications for the diagnosis treatment for various human diseases. A simple and rapid assay method for ADA, based on the enzymatic formation of a luminescent lanthanide complex, is proposed in this study. Inosine, an enzymatic product of ADA with stronger sensitization efficiency for Tb³⁺ than adenosine, produced a strong luminescence by forming an inosine-Tb³⁺ complex, and it enabled the direct monitoring of ADA activity in real-time. By introducing only Tb³⁺ to adenosine and ADA in the buffer, the enhancement of luminescence enabled the detection of a low concentration of ADA (detection limit 1.6 U/L). Moreover, this method could accurately determine the inhibition efficiency (IC₅₀) of the known ADA inhibitor, erhythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), and the inhibition of ADA could be confirmed by the naked eye. Considering its simplicity, this assay could be extended to the high-throughput screening of various ADA inhibitor candidates.

Development of a rapid, microplate-based kinetic assay for measuring adenosine deaminase activity in body fluids

BACKGROUND

Adenosine deaminase (ADA) catalyzes the deamination of adenosine to inosine. The activity of ADA in body fluids has clinical utility in the assessment of suspected tuberculosis.

METHODS

The conversion of adenosine to inosine was monitored in 96-well microplates as a continuous decrease at 265 nm for 15 min at ambient temperature. Analytical precision, sensitivity, linearity, accuracy, and enzyme stability were validated. Reference intervals were established from >120 tuberculosis-negative pleural, peritoneal, and cerebrospinal fluid samples.

RESULTS

The molar extinction coefficients of adenosine and inosine at 265 nm were 12,715 and 4,918 l/mol.cm and their difference was used to calculate ADA activity. Maximum within-day imprecision was <11% and maximum total precision was <19%. Analytical sensitivity was 0.5 U/l and the assay was linear to 40 U/l. ADA recovery was 96-110% over an activity range of 11.7-25.3 U/l. ADA was stable for 1, 7 and 30 days at ~25 °C, 4-8 °C, and -20 °C storage, respectively. Upper reference limits were 9.4, 7.3, and 1.5 U/l for pleural, peritoneal, and cerebrospinal fluid, respectively.

CONCLUSIONS

The microplate-based kinetic ADA assay has favorable performance characteristics. This method eliminates the need for assay calibration and allows 96 samples to be tested simultaneously.

Adenosine deaminase in the pig: tissue-specific patterns and expression of the silent ADA0 allele in nucleated cells

By means of polyacrylamide gel and cellulose acetate enzymo-electrophoresis, the authors have studied tissue-specific isozymes of adenosine deaminase in the pig; these have been correlated to the erythrocytic ABO-like polymorphism. The enzyme product of the ADA0 gene was detected in nucleated cells; the absence of the ADA0 gene product in erythrocytes was tentatively accounted for by an increased in vivo lability.

Effect of cardiovascular drugs on adenosine deaminase activity

OBJECTIVE

Adenosine deaminase catalyzes the conversion of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. Because raising adenosine concentration can affect several physiological processes we studied the effect of a selection of cardiological drugs on adenosine deaminase activity in red blood cells and rabbit plasma after 21 days administration.

METHODS AND RESULTS

We determined the activity of adenosine deaminase isoenzymes (ADA(1) and ADA(2)). Simvastatin, aspirin, metoprolol, and isosorbide mononitrate significantly decreased plasma total adenosine activity (by 50%, 34%, 29%, and 19%, respectively; P < .05 to P < .001) mainly by decreasing the activity of ADA(2).

CONCLUSIONS

As a consequence of decreased ADA(2) activity , the half-life of adenosine will be lengthened. This may, at least in part, explain some of the beneficial effects of analyzed drugs. Our results might be clinically relevant in patients with coronary artery disease, acute coronary syndromes, heart failure, or stroke where the investigated drugs are commonly used. However, our results should be confirmed in large studies in humans.

Further data on adenosine deaminase polymorphism in pigs and evidence for a new allele

Evidence was provided for a new erythrocyte ADA allele (Aw) in the Swedish Landrace breed of pigs. The enzyme activity of Aw variant was considerably less than that of the previously reported erythrocyte ADA variants A and B. The mobility of the Aw variant was identical to that of the A variant, both by electrophoresis and by isoelectric focusing. The in vitro heat stability (at 56 degrees C) of the Aw variant was similar to that of A and B variants. The leucocyte ADA activity was normal in pigs with the erythrocyte ADA Aw variant. The frequencies of the erythrocyte ADA alleles, A, B, Aw, and O (silent allele) in four breeds of pigs in Sweden were: Landrace--0.51, 0.19, 0.11, 0.19; Large White--0.91, 0.03, 0.0, 0.06; Duroc--0.95, 0.05, 0.0, 0.0; Hampshire--0.12, 0.14, 0.0, 0.74.

Changes in adenosine deaminase activity in ageing cultured human cells and the role of zinc

The level of adenosine deaminase (ADA; EC 3.5.4.4) was estimated at different passages in six confluent fibroblast cultures established from forearm skin biopsies of healthy adult normal volunteers. After determination of the zinc concentration in standard growth medium, ADA activity was estimated at different passages of subculture in media with different zinc concentrations. The results indicated that the specific activity of ADA in control confluent skin fibroblast cultures (passage 2) cultivated in standard growth medium containing 15.4 microM zinc (similar to that present in normal human plasma) was equal to 226.6+/-19.64 micromol min(-1) mg(-1) protein. The results showed that there were no significant changes in ADA specific activity in any of the control cultures as the zinc concentration of the medium was increased. To characterize the passage of subculture at which fibroblasts enter the ageing phase, three marker enzymes were assayed namely, phosphofructokinase, lactate dehydrogenase and glycogen phosphorylase. The result showed that the cells enter the ageing phase at passage 20 and beyond. Further investigation showed that ADA activity of serially subcultured confluent cultures cultivated in standard growth medium significantly dropped at passages 20, 25 and 30. ADA activity however was not significantly altered in cells at passage 2, 10 and 15 cultivated in standard growth medium and in the presence of higher zinc levels (23.1, 34.6, 53.8 and 73.1 microM). Furthermore there was significant lowering of ADA activities in cells at passages 20, 25 and 30 when cells were cultured in the presence of 15.4, 23.1 and 34.6 microM zinc. Such lowered activities of ADA were restored to normal when the cells were cultured in the presence of higher zinc concentration equal to 53.8 and 73.1 microM. From the results we concluded that it is possible to restore ADA activity in aged skin fibroblasts to normal levels by raising the zinc concentration in the culture medium to four or five times the control normal plasma zinc level.

Purine nucleoside phosphorylase deficiency: a new case report and identification of two novel mutations (Gly156A1a and Val217Ile), only one of which (Gly156A1a) is deleterious

Purine nucleoside phosphorylase (PNP) deficiency results in an autosomal recessive immunodeficiency disease characterized by initial involvement of cellular immunity and neurological manifestations with subsequent abnormalities of humoral immunity. The initial presentation and clinical course has varied widely in the relatively few published cases. The molecular basis has been reported in only 10 patients, precluding evaluation of phenotype-genotype relationships. We now report clinical, immunologic, and molecular findings in a new case of relatively early onset that emphasizes hypotonia and developmental delay as early manifestations. The patient carried two novel missense mutations (Gly56A1a and Val217Ile) on the same allele in apparent homozygosity. Expression of each of the mutant enzymes in vitro demonstrated that the Gly156A1a mutation abolished enzyme activity while the Val217Ile mutation was without obvious effect and is therefore a normal variant. Such "normal" polymorphisms might be associated with a variable response to the immunosuppressive PNP inhibitors currently in clinical trials.

Common resistance mechanisms to deoxynucleoside analogues in variants of the human erythroleukaemic line K562

Resistant variants of the human leukaemic line K562 were developed using selection with the deoxynucleoside analogues cytosine arabinoside, 2-chlorodeoxyadenosine, fludarabine and gemcitabine. The resistant lines displayed a high degree of cross resistance to all deoxynucleoside analogues, with little or no cross resistance to other agents. There was a profound accumulation defect of all nucleoside analogues in the resistant variants but no significant defect in nucleoside transport in any of the variants. 5' nucleotidase activity was strongly increased and deoxycytidine kinase activity was moderately reduced in all of the resistant variants, resulting in reduced accumulation of triphosphate analogues. In addition a deletion in one of the alleles of the deoxycytidine kinase was detected in the fludarabine-resistant line. Ribonucleotide reductase activity was found to be strongly increased in the gemcitabine-selected line and purine nucleoside phosphorylase was increased in the 2-chlorodeoxyadenosine-selected line. Free nucleotide pools were increased in the 2-chlorodeoxyadenosine-selected line. There was no expression of the mdr1 gene by the resistant lines. Karyotypic analysis and FISH experiments using a 6q21 specific probe showed alterations in the 6(q16-q22) region which contains the 5'-nucleotidase gene. Early events in the activation and degradation of deoxynucleoside analogues appear to constitute common mechanisms of resistance to these compounds.

Determination of the kinetic parameters of adenosine deaminase by electrophoretically mediated microanalysis

The possibility of determining the Michaelis constant of the irreversible deamination of adenosine to inosine by adenosine deaminase, using capillary electrophoresis, was investigated. This paper describes the use of electrophoretically mediated microanalysis (EMMA) as the technique for carrying out the assay. Initial reaction velocities of the enzymatic reaction were estimated from the peak area of inosine, and the Michaelis constant was calculated according to the Lineweaver-Burk equation. The result (Km = 5.3 x 10(-5) M +/- 8 x 10(-6) M) was consistent with previously reported values. Using the present method, a total amount of as few as 1.2 fmole of enzyme and 9.2 ng of substrate were injected in the capillary for the construction of a Michaelis Menten curve (seven concentrations of substrate, each concentration analyzed in triplicate), which is far smaller than the quantities required in conventional methods.

Biologic Relevance of Elevated Red Cell Adenosine Deaminase Activity in Myelodysplastic Syndromes and Paroxysmal Nocturnal Hemoglobinuria

Red cell adenosine deaminase (ADA-RBC) activity in patients with myelodysplastic syndromes and paroxysmal nocturnal hemoglobinuria is significantly increased compared to that observed in normal controls. ADA-RBC activity is not related to fetal hemoglobin concentration, but it is significantly correlated with hemoglobin concentration at diagnosis and with the degree of morphologic dysplasia in the erythroid lineage. The results of our study suggest that the observed enzymatic abnormality may constitute a non-specific manifestation of the stem cell alteration that determines these disorders.

Lymphocyte adenosine deaminase activity (L-ADA) in leprosy, during and after treatment of reactions

Twenty-five patients with type 1 (lepra) and type 2 (E.N.L.) leprosy reactions were studied for lymphocyte adenosine deaminase activity (L-ADA), during and after treatment of the reactions, using a standard technique, in order to establish its pattern and if possible, its value in assessing the course of reactions. The results were compared with those from 30 control subjects, comprising 10 normal healthy adults, 10 patients with borderline tuberculoid (BT) leprosy, four patients with borderline lepromatous (BL) leprosy and six patients with lepromatous (LL) leprosy. The level of L-ADA in the leprosy controls was higher than that of normal healthy subjects. The L-ADA values in patients with different types of reactions were about 10-fold higher than those obtained from leprosy controls, emphasizing a possible role in assessing reactions in leprosy. However, there was no significant variation in L-ADA levels, either between the various leprosy controls or reaction groups, before and after treatment.

Deficiency of purine nucleoside phosphorylase activity in thymocytes from the immunodeficient diabetic BB rat

The spontaneously diabetic BB (BBd) rat displays marked T lymphopenia. The present study was designed to investigate whether the immunodeficiency in this animal may be associated with deficiency of purine nucleoside phosphorylase (PNP) and possibly adenosine deaminase (ADA). The activities of these two enzymes were measured in lymphoid and non-lymphoid cells from both non-diabetes-prone (BBn) and BBd rats as well as from streptozotocin-induced diabetic (STZ) BBn rats. There were no significant differences between BBn and BBd rats in ADA activities in thymocytes, skeletal muscle or brain. However, ADA activity was increased (P less than 0.01) by 50% in BBd mesenteric lymph node lymphocytes and splenocytes as compared with BBn cells, but was not altered in cells from STZ-BBn rats. On the other hand, the PNP activity in BBd thymocytes was only 61% (P less than 0.01) of that observed in BBn cells. This PNP deficiency was not the consequence of diabetes per se, as its activity was normal in thymocytes from STZ-BBn rats. There were no significant differences in PNP activities between BBn and BBd rats in all other cell types examined. The diabetic BB rat may be a novel source of PNP-deficient thymocytes (mainly immature T cells) for studying biochemical mechanisms of immunodeficiency in association with decreased PNP activity. The findings also raise the question of whether a causal relationship exists between PNP deficiency and the recently demonstrated abnormality in T cell maturation in the thymus of the BBd rat.

Adenosine deaminase in body fluids: a useful diagnostic tool in tuberculosis

The performance of a colorimetric ADA determination in body fluids other than serum in the diagnosis of tuberculosis was assessed in 1063 patients from whom pleural (600), peritoneal (136), pericardial (77), or cerebrospinal (250) fluids were obtained. In exudative pleuroperitoneal and pericardial effusions, an ADA decision level of 0.71 mu kat/L displayed a sensitivity of 1.00, and was higher than those of histologic (0.83) and bacteriologic (0.62) studies. At this level, ADA reached a specificity of 0.92 and efficiency of 0.94. In cerebrospinal fluid, an ADA catalytic concentration above 0.15 mu kat/L strongly suggests tuberculous meningitis in patients older than 7 years (sensitivity 1.00, specificity 0.99 and efficiency 0.99). ADA results obtained with a UV-method were closely correlated with those of the colorimetric method in pleuroperitoneal effusions (r = 0.989) and in cerebrospinal fluids (r = 0.905). Sample blanks should be processed, otherwise false positive results may be found in non-tuberculous cerebrospinal fluids (5.3%) and pleuroperitoneal effusions (3.8%).

Adenosine deaminase in stroma-free hemoglobin solution is not responsible for coronary vasoconstriction

Erythrocytes contain a high concentration of cytosolic adenosine deaminase and this enzyme activity is present in preparations of stroma-free hemoglobin (SFHS). The documented vasoconstrictor activity of SFHS preparations does not appear to be due to interference with endogenous adenosine-mediated mechanisms, because removal of greater than 80% of adenosine deaminase activity failed to affect the vasoconstrictor potency of SFHS preparations. We have also demonstrated the presence of a contractility-depressant activity in SFHS when the latter was added to aqueous buffer perfusing rat Langendorff-hearts. This activity is diminished in phosphocellulose-purified preparations with reduced adenosine deaminase activity but is not necessarily causally related to this enzyme.

The map of chromosome 20

The number of gene assignments to human chromosome 20 has increased slowly until recently. Only seven genes and one fragile site were confirmed assignments to chromosome 20 at the Ninth Human Gene Mapping Workshop in September 1987 (HGM9). One fragile site, 13 additional genes, and 10 DNA sequences that identify restriction fragment length polymorphisms (RFLPs), however, were provisionally added to the map at HGM9. Five mutated genes on chromosome 20 have a relation to disease: a mutation in the adenosine deaminase gene results in a deficiency of the enzyme and severe combined immune deficiency; mutations in the gene for the growth hormone releasing factor result in some forms of dwarfism; mutations in the closely linked genes for the hormones arginine vasopressin and oxytocin and their neurophysins are probably responsible for some diabetes insipidus; and mutations in the gene that regulates both alpha-neuraminidase and beta-galactosidase activities determine galactosialidosis. The gene for the prion protein is on chromosome 20; it is related to the infectious agent of kuru, Creutzfeld-Jacob disease, and Gertsmann-Straussler syndrome, although the nature of the relationship is not completely understood. Two genes that code for tyrosine kinases are on the chromosome, SRC1 the proto-oncogene and a gene (HCK) coding for haemopoietic kinase (an src-like kinase), but no direct relation to cancer has been shown for either of these kinases. The significance of non-random loss of chromosome 20 in the malignant diseases non-lymphocytic leukaemia and polycythaemia vera is not understood. Twenty-four additional loci are assigned to the chromosome: five genes that code for binding proteins, one for a light chain of ferritin, genes for three enzymes (inosine triphosphatase, s-adenosylhomocysteine hydrolase, and sterol delta 24-reductase), one for each of a secretory protein and an opiate neuropeptide, a cell surface antigen, two fragile sites, and 10 DNA sequences (one satellite and nine unique) that detect RFLPs.

Metabolic and functional consequences of inhibiting adenosine deaminase during renal ischemia in rats

The concentrations of renal ATP have been measured by 31P-nuclear magnetic resonance (NMR) before, during, and after bilateral renal artery occlusion. Using in vivo NMR, the initial postischemic recovery of ATP increased with the magnitude of the residual nucleotide pool at the end of ischemia. ATP levels after 120 min of reflow correlated with functional recovery at 24 h. In the present study the effect of blocking the degradation of ATP during ischemia upon the postischemic restoration of ATP was investigated. Inhibition of adenosine deaminase by 80% with the tight-binding inhibitor 2'-deoxycoformycin led to a 20% increase in the residual adenine nucleotide pool. This increased the ATP initial recovery after 45 min of ischemia from 52% (in controls) to 62% (in the treated animals), as compared to the basal levels. The inhibition also caused an accelerated postischemic restoration of cellular ATP so that at 120 min it was 83% in treated rats vs. 63% in untreated animals. There was a corresponding improvement in the functional recovery from the insult (increase of 33% in inulin clearance 24 h after the injury). Inhibition of adenosine deaminase during ischemia results in a injury similar to that seen after a shorter period of insult.

Elevated erythrocyte adenosine deaminase activity in a patient with primary acquired sideroblastic anemia

We report a case of primary acquired sideroblastic anemia (PASA) associated with elevated erythrocyte adenosine deaminase (ADA) activity. The patient was an 85-year-old Japanese male. Analysis of the peripheral blood revealed pancytopenia, and the bone marrow findings showed marked ringed sideroblasts and chromosomal deletion (46XY, 11q-). The erythrocyte ADA activity was 17 times higher than that of normal control, the leukocyte ADA activity was within the normal range, and the plasma ADA activity was 2 times higher than the normal mean. The adenine nucleotides in the patient's erythrocytes were within normal range. According to starch gel electrophoresis, ADA isozyme of the patient was ADA 1. Western blotting showed an increased amount of ADA protein in the patient's erythrocytes. Southern blotting revealed no gene amplification or large structural change. Dot blot analysis of the reticulocyte mRNA showed no increase in the amount of ADA mRNA in the patient's reticulocytes compared with those of reticulocyte-rich controls. We considered that the mechanism of elevated ADA activity in this acquired defect was similar to that found in hereditary hemolytic anemia associated with ADA overproduction.

Elevated red cell adenosine deaminase activity: a marker of disordered erythropoiesis in Diamond-Blackfan anaemia and other haematologic diseases

Red-cell adenosine deaminase (ADA) activity in children with Diamond-Blackfan anaemia is significantly increased (1.91 +/- 0.90 U/g Hb) compared to that seen in transient erythroblastopenia of childhood (0.80 +/- 0.16 U/g Hb) or normal individuals (0.61 +/- 0.13 U/g). These data thus further support that measurement of this purine metabolic enzyme is useful in diagnosing the cause of pure RBC aplasia in children. Of interest, however, elevated RBC-ADA activity also is seen in some children with acute leukaemia and other haematologic disorders. In children with acute lymphoblastic leukaemia (ALL), the increase in RBC-ADA activity is proportional to the degree of anaemia. However, the elevated RBC-ADA activity in this leukaemic population is not related to the fetal haemoglobin concentration. These data suggest increased RBC-ADA activity may be a non-specific manifestation of abnormal erythroid stem cell function, an alteration distinct from that seen with reactivation of fetal erythropoiesis. However, since almost all patients with Diamond-Blackfan anaemia manifest elevated RBC-ADA activity, this chemical alteration yet may reflect the specific erythroid differentiation lesion in this disorder.

Comparative activity of erythrocyte adenosine deaminase and orotidine decarboxylase in Diamond-Blackfan anemia

It previously has been reported that red blood cells (RBC) of patients with Diamond-Blackfan syndrome (DBS) have increased activity of orotidine decarboxylase (ODC) and adenosine deaminase (ADA). The studies reported here compared the activity of these two enzymes in DBS erythrocytes, cord blood, and reticulocytes. The activity of ODC, although increased in some DBS erythrocytes, was not significantly different from that seen in cord RBC or reticulocytes. In contrast, RBC-ADA activity was increased in 23 of 26 DBS patients; and this enzyme elevation was distinct from that seen in cord blood and reticulocytes. Moreover, ADA activity was normal in 26 of 27 patients with transient erythroblastopenia of childhood (TEC). Taken together, these data indicate RBC-ADA activity is more sensitive than ODC as a marker of DBS. In addition, RBC-ADA activity continues to be useful for distinguishing DBS and TEC in most patients with RBC hypoplasia.

Prenatal exclusion of purine nucleoside phosphorylase deficiency

We report on the prenatal exclusion of purine nucleoside phosphorylase (PNP) deficiency in a fetus whose parents were known to be heterozygotes for the enzyme defect. Prenatal investigation was performed in the 16th week of gestation on amniotic fluid and cultured amnion cells using sensitive techniques. The results suggested that the fetus was either normal or a heterozygote. PNP activity in cord red cells confirmed the heterozygous status of the baby.

Deficiency of adenosine deaminase in the wasted mouse

Wasted (wst) is a spontaneous mutation with autosomal recessive inheritance. Abnormally low levels of adenosine deaminase have been found in erythrocytes from the wasted mouse. Enzyme activity in wst/wst mice is reduced to 38% of that found in the erythrocytes from control mice, and the apparent Km for adenosine is reduced to 51% of control. These changes imply an alteration in the catalytic properties of the enzyme arising from a change in the primary structure of the protein. We postulate that wasted is a mutation in the structural gene for adenosine deaminase. In man, the autosomal recessive form of severe combined immunodeficiency is associated, in about one-third of cases, with a deficiency of adenosine deaminase. Wasted mice are immunodeficient, develop neurological abnormalities, and die soon after weaning. These features are shared with the human syndrome. We therefore further suggest that the wasted mouse is an animal model for this form of severe combined immunodeficiency that will have potential use in gene-therapy studies.

Molecular aspects of erythroenzymopathies associated with hereditary hemolytic anemia

Since the discovery of glucose 6-phosphate dehydrogenase (G6PD) and of pyruvate kinase deficiencies, erythroenzymopathies associated with hereditary hemolytic anemia have been extensively investigated. Kinetic and electrophoretic studies have shown that most, if not all, erythroenzymopathies are caused by the production of a mutant enzyme. Except for a few enzymes that are abundant in blood and tissues, it is difficult to obtain enough sample to study the functional and structural abnormalities of mutant enzymes associated with genetic disorders in man. The primary structures of only two normal red cell enzymes which can cause hereditary hemolytic anemia, phosphoglycerate kinase (PGK) and adenylate kinase, have been determined. Single amino acid substitutions of PGK variants have been found, and the identification of the exact molecular abnormalities of such variants has helped us to understand the accompanying functional abnormality. Gene cloning makes possible the identification of the DNA sequence that codes for enzyme proteins. Recently, human complementary DNA (cDNA) for aldolase, PGK, G6PD, and adenosine deaminase (ADA) have been isolated, and the nucleotide sequences for PGK and ADA determined. In the near future, human cDNA sequencing should permit identification of the gene alteration that gives rise to the mutant enzymes.

Adenosine deaminase gene amplification in deoxycoformycin-resistant mammalian cells

Deoxycoformycin (dCF)-resistant mutants of rat hepatoma, mouse LMTK-, and Chinese hamster ovary (CHO) cells have been isolated and shown to overproduce adenosine deaminase (ADA). The overproduction of ADA was found to be due to ADA-gene amplification in rat and mouse cells but not in CHO cells. Deoxycoformycin-resistant rat hepatoma cells have large HSRs (homogeneously staining regions), mouse cells carry DMs (Double minutes), and CHO cells do not appear to have any gross chromosomal anomalies. When dCF-resistant rat hepatoma and mouse cells are selected by increasing the concentration of the inhibitor in small increments, there is a good correlation between the increase in ADA gene copy number and the increase in the level of expression of ADA, suggesting that all of the amplified genes are equally active in the expression of ADA.

Adenosine deaminase (ADA) in leukemia: clinical value of plasma ADA activity and characterization of leukemic cell ADA

Adenosine deaminase (ADA) activity was measured in plasma, erythrocytes, and mononuclear cells from 18 patients with acute and chronic leukemia. High levels of ADA activities were found in plasma, erythrocytes, and mononuclear cells from patients with acute leukemia, especially acute lymphoblastic leukemia, and blastic crisis of chronic myeloid leukemia. Serial determination of plasma ADA activities was done in 9 patients with acute leukemia. All patients untreated or in relapse had an elevation of plasma ADA activity, which decreased to normal or subnormal levels during complete remission. On starch gel electrophoresis, plasma ADA in leukemic patients separated into two bands. The major band showed a mobility identical to that of normal red cells and mononuclear cells, and the minor band corresponded to that of normal plasma ADA. Enzymatic and immunological studies were performed on ADA from leukemic cells of acute myeloid and lymphoblastic leukemia. There were no differences in Michaelis constant for adenosine, thermostability, electrophoretic mobility, immunological reactivity, and specific activity between ADA of leukemic cells and normal mononuclear cells. These results strongly suggest that the increased ADA activity in leukemic cells is caused by an increased synthesis of a structurally normal enzyme and that increased plasma ADA activity in leukemic patients reflects an increment of leukemic cells in bone marrow. Therefore, serial determination of plasma ADA activities seems to provide a good indicator of the total mass of leukemic cells in bone marrow.

An approach to a selection system for adenosine-deaminase-positive (ADA+) cells and detection of rat ADA+ "revertants"

We have substituted deoxyadenosine or adenosine for hypoxanthine in the standard HAT selection system in an attempt to select for ADA-normal (ADA+) cells. ADA- human lymphoid line cells could not utilize deoxyadenosine as an alternative to hypoxanthine as a purine source (DAT) and failed to grow but were only somewhat inhibited in growth when adenosine was substituted for hypoxanthine (AAT). In contrast, ADA+ cells utilized adenosine or deoxyadenosine as efficiently as hypoxanthine as a purine source. Growth in DAT, but not in HAT, of an artificial mixture of one ADA+ human lymphoid cells in 1,000 ADA- cells resulted in enrichment of ADA+ cells to 25-86% of total cells. When we grew a rat ADA- cell line in two variations of the DAT system, we detected at least three electrophoretically different ADA+ patterns, one of which corresponded to normal rat ADA. These could represent "revertants."

Alteration of adenosine deaminase levels in peripheral blood lymphocytes of patients with gastric cancer

The present study was undertaken to determine the adenosine deaminase (ADA) activity of peripheral lymphocytes in patients with gastric cancer, with respect to the cancer progression, the effect of surgery and/or immunotherapy. The gastric cancer patients showed lower lymphocyte ADA activity than did the normal control. The lymphocyte ADA activity did not decrease with the cancer progression. There was a significant correlation between lymphocyte ADA activity and blastogenesis of lymphocyte by phytohemaglutinin or concanavalin A. Six months following gastrectomy, the lymphocyte ADA activity was increased, as compared with the preoperative value. The ADA activity of patients on post-operative OK-432 showed a greater increase, as compared to that of patients not given this treatment. In conclusion, decreased lymphocyte ADA activity in gastric cancer patients might be due to either the cancer bearing status or to the immunological suppression.

Prenatal diagnosis of a true mosaic trisomy 20 substantiated by demonstration of a gene dosage effect for adenosine deaminase (ADA)

Fibroblasts from a fetus with the prenatal diagnosis of mosaic trisomy 20 were cloned by dilution plating. Adenosine deaminase (ADA), a biochemical marker for chromosome 20, was assayed in trisomic clones and normal clones as control. The cytogenetic diagnosis was substantiated by demonstration of a triplex gene dosage effect for ADA in the trisomic cells.

Transfusion-associated acquired immune deficiency syndrome in infants

Two preterm infant boys not known to be at risk developed clinical, laboratory, and pathologic features of acquired immune deficiency syndrome (AIDS) after receiving multiple blood transfusions in the neonatal period. Their clinical courses were characterized by failure to thrive, recurrent otitis media, hepatomegaly, and fatal interstitial pneumonia. Laboratory evaluation revealed progressive lymphopenia, reversed T helper/suppressor ratios, increased percentages of B-lymphocytes, decreased lymphoproliferative responses to mitogens, hyperimmunoglobulinemia, and high levels of circulating immune complexes. At postmortem examination thymic involution, lymphocyte depletion in spleen and lymph nodes, and micronodular mineralization in the central nervous system were seen. The findings were not specific for other known congenital immune deficiencies and were most indicative of AIDS. The lack of other risk factors suggests transmission of AIDS via blood transfusions in the neonatal period.

Immune deficiency due to adenosine deaminase and purine nucleoside phosphorylase deficiency: a simple diagnostic test

A simple method is described for diagnosing adenosine deaminase and purine nucleoside phosphorylase deficiency using urine. Cellulose thin layer chromatography of 1 microliter of urine from affected children was performed and deoxyadenosine and deoxyguanosine were easily detected by phosphorescence at the temperature of liquid nitrogen. This test is not expensive and can be done in any laboratory. It should be suitable for diagnostic screening in patients with immune deficiency.

Mechanism of inhibition of phosphoribosylation of 5-fluorouracil by purines

The mechanism of the abolishment of the cytotoxicity of 5-flurouracil by purines in L5178Y cells was determined by using phosphoribosylation enzymes for both 5-fluorouracil and hypoxanthine. Hypoxanthine inhibited the phosphoribosylation of 5-fluorouracil in the presence of both enzymes, but no inhibition by hypoxanthine was found without hypoxanthine phosphoribosyltransferase or at a high concentration of 5-phosphoribosyl 1-pyrophosphate (PRPP). Hypoxanthine, adenine and inosine decreased the intracellular concentration of PRPP to less than one-tenth of that of the control. These results suggest that 5-fluorouracil is activated directly to its nucleotide, 5-fluorouridine 5'-monophosphate, by the phosphoribosylation enzyme and that the inhibition of activation by purines is due to depletion of PRPP.

Enzymes of purine metabolism in B-chronic lymphocytic leukemia

In order to study if enzymes of purine metabolism could be used as cell markers in B-chronic lymphocytic leukemia (B-CLL), the activities of adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and 5'-nucleotidase (5'N) were repeatedly measured in blood mononuclear cells from B-CLL patients and were compared to those obtained in normal controls. Enzyme activities in patients were also compared to other biological parameters indicative of B-CLL to activities of ADA and PNP in erythrocytes. Results show that B-leukemic cells display abnormal enzyme patterns: subnormal ADA activity is characteristic; 5'N activity is depressed in 60% of the cases but increased in 15%. An inverse relationship between PNP activity and corresponding lymphocytosis is observed in leukemic but not in normal cells. The enzymatic anomalies seem to be linked to the presence of an unusual peripheral lymphocytic population, induced by the leukemic process. Indeed, ADA and PNP are not abnormal in erythrocytes. In untreated nonevolutive patients, the enzyme profile tends to remain stable throughout the course of the illness; normalization of enzyme patterns in treated patients occurs only when therapy induces improvement in T and B cell distribution.

An enzymatic kinetic method for the determination of 2'-deoxycoformycin in biological fluids

An analytical method for determination of 2'-deoxycoformycin (2'-DCF) concentrations in plasma and urine was developed based upon a modification of adenosine deaminase (ADA) inhibition assays described in the literature. The method involves the spectrophotometric monitoring of the rate of deamination of adenosine by the enzyme in the presence of various concentrations of the inhibitor 2'-DCF, and relating the deamination rate to the 2'-DCF concentration. In the course of developing the method, it was found that adenosine deaminase appears to lose activity after dilution with phosphate buffer (pH 7.2). Enzyme inactivation was found to occur mono-exponentially with time and, in order to accommodate for this inactivation, a method was developed for quantitating 2'-DCF which takes into consideration the relative activity of the enzyme in the incubation mixtures. The results obtained from the analysis of samples containing known concentrations of 2'-DCF were fitted to a three-dimensional standard surface by means of a nonlinear least-squares regression computer program. Quantitation of 2'-DCF in patient samples is accomplished by an ADA inhibition titration technique in which the spectrophotometrically determined absorbance change is related to the two independent variables, the concentration of 2'-DCF in the standards and the relative time of the analysis. As little as 1 ng/ml of 2'-DCF in plasma can be quantitated with the assay.

Elevated erythrocyte adenosine deaminase activity in congenital hypoplastic anemia

Abnormalities of adenosine deaminase, a critical enzyme of the purine salvage pathway, have been reported in association with immune dysfunction, acute leukemia, and hereditary hemolytic anemia. We report data showing that erythrocyte adenosine deaminase activity is also abnormal in congenital hypoplastic anemia (the Diamond-Blackfan syndrome). Adenosine deaminase activity in erythrocytes from 12 patients (mean +/- S.D., 2.20 +/- 0.77 IU per gram of hemoglobin) was substantially greater than that observed in 50 controls (0.62 +/- 0.13 IU per gram). Enzyme activity in affected patients was also greater than that seen in cord blood or in erythrocytes from patients with hemolytic anemia, acquired aplastic anemia, Fanconi's hypoplastic anemia, acquired pure red-cell aplasia, or transient erythroblastopenia of childhood. These observations indicate that erythrocyte adenosine deaminase activity may be a unique marker for identifying congenital hypoplastic anemia.