Characteristics and significance of the reverse glucose-6-phosphate dehydrogenase reaction

Glucose-6-phosphate dehydrogenase (G-6-PD) is the first enzyme of the hexose monophosphate pathway, and this important reaction is often considered to be irreversible. However, its apparent irreversibility is caused by the rapid removal of the immediate product, 6-phosphoglucono-delta-lactone. We have now investigated the reverse G-6-PD reaction, namely, the oxidation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) by 6-phosphoglucono-delta-lactone to form glucose-6-phosphate and nicotinamide-adenine dinucleotide phosphate (NADP). The substrate of the reaction, 6-phosphoglucono-delta-lactone, was rapidly generated from glucose-6-phosphate and NADP. The lactone was stabilized by addition of perchloric acid. A substrate analogue, 6-phosphoglucono-gamma-lactone, was synthesized by dehydrating 6-phosphogluconic acid. At pH 2.3 the t 1/2 of the delta-lactone was 2.4 hours; that of the gamma-lactone was 57 hours. The following kinetic parameters were established: Km delta-lactone 1027 +/- 183 mumol/L; Km gamma-lactone 266 +/- 71 mumol/L; Km NADPH less than 10 mumol/L; ratio of the Vmax G-6-PD forward/reverse reaction 2.0. Glucose-6-phosphate was found to be a competitive inhibitor with both lactones in the reverse G-6-PD reaction. Genetic mutants of humans in which the Km of G-6-PD for glucose-6-phosphate was diminished also had a diminished Km for 6-phosphoglucono-delta-lactone. Thus, it appears that the same active site on the enzyme binds glucose-6-phosphate in the forward reaction and 6-phosphogluconolactone in the reverse reaction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glucose-6 phosphate dehydrogenase deficiency: an easy and sensitive quantitative assay for the detection of female heterozygotes in red blood cells

Different methods for the quantitative determination of glucose-6-phosphate dehydrogenase (G-6-PD) were compared and one of them found to be highly precise. Maleimide inactivation of 6-phosphogluconate dehydrogenase (PGD) was investigated. It was shown that this inactivation is time-dependent and causes loss of assay precision. The most precise method was adapted to lysates of red blood cells from females, known to be heterozygote for G-6-PD deficiency and from non-deficient males and females. Heterozygote gene carriers were detected at a rate of 97.0%.     

新生儿葡萄糖-6-磷酸脱氢酶缺乏症的筛查与分析

目的通过对新生儿葡萄糖-6-磷酸脱氢酶（glucose-6-phosphate dehydrogenase,G-6-PD）缺乏症的筛查及临床分析,了解桂平市新生儿G-6-PD缺乏情况及G-6-PD缺乏幼儿与高胆红素血症的相关性。方法对2010年7月至2011年7月在该院出生的3 402例新生儿进行G-6-PD测定,统计分析G-6-PD缺乏情况,并跟踪回访新生儿至出生后第10天,如果出现黄疸应立即采血测定胆红素,对新生儿高胆红素血症的发生率进行比较分析。结果新生儿G-6-PD缺乏症发病率为10.35%（352/3 402）,男婴G-6-PD缺乏率为14.28%（264/1 849）;女婴G-6-PD缺乏率为5.66%（88/1 553）。G-6-PD缺乏幼儿高胆红素血症的发生率为25.3%,明显高于G-6-PD正常新生儿的2.6%（P〈0.01）。结论广西桂平市是G-6-PD缺乏症的高发区,对G-6-PD缺乏症的筛查非常有意义,能有效提示医生谨慎用药和指导患儿避免接触诱因,预防溶血的发生,提高该地区人群的健康素质。     

Association of Naphthalene with Acute Hemolytic Anemia

OBJECTIVES: To describe the prevalence and severity of naphthalene-associated hemolysis (NA1) and infection-associated hemolysis (IAH) in children with glucose-6-phosphate dehydrogenase (G6-PD) deficiency. To survey the rationale for naphthalene-containing moth repellent (mothball) use in the study population and to compare this with that of a more diverse population. METHODS: A ten-year retrospective chart review of 160 patients with G-6-PD deficiency and/or anemia and an analysis of 24 hospitalized African-American children with an episode of acute hemolysis associated with G-6-PD deficiency were conducted. The parents of 330 children cared for in the pediatric emergency departments (EDs) of two tertiary care centers were questioned regarding domestic mothball (naphthalene) use. RESULTS: Fourteen of 24 (58.3%) of the children identified with G-6-PD deficiency presented with hemolysis associated with exposure to naphthalene-containing moth repellents. The remaining ten had IAH. Seventy-nine percent of the NAH group required transfusion, compared with 60% of the IAH group. Mothballs were reportedly used by 27% of the families surveyed in one inner-city population with a 2-13% incidence of G-6-PD deficiency and by 15% in a more culturally diverse city. The main reported motivation for use was the fresh scent, not as a moth repellent. CONCLUSIONS: Mothballs are used for previously unrecognized reasons. Naphthalene-containing mothballs can pose a hematologic threat to vulnerable populations.     

Detection of glucose-6-phosphate dehydrogenase deficiency in erythrocytes: a spectrophotometric assay and a fluorescent spot test compared with a cytochemical method

The results of a quantitative spectrophotometric enzyme assay, a fluorescent spot test and a cytochemical assay for glucose-6-phosphate dehydrogenase deficiency were compared systematically. The high sensitivity of the spectrophotometric assay and the fluorescent spot test in the detection of severely deficient individuals was confirmed. For the detection of heterozygote females, however both tests were unreliable; the sensitivities of the fluorescent spot test and the spectrophotometric assay being 32% and 11% respectively. Specificities for both tests were high (99%). Introduction of the ratio of glucose-6-phosphate dehydrogenase and pyruvate kinase (G-6-PD/PK ratio) activities increased the sensitivity of the spectrophotometric assay to nearly 100%. It is concluded that the fluorescent spot test should be used for the diagnosis of G-6-PD deficiency in developing countries; whereas if spectrophotometric enzyme assays are available, the G-6-PD/PK ratio should always be performed. In cases where the ratio is less than 0.70, cytochemical analysis is indicated.     

Mass screening for glucose-6-phosphate dehydrogenase deficiency: improved fluorescent spot test

New data on the reliability of the fluorescent spot test are presented. Improvements in the assay were established. Newborn mass screening for glucose-6-phosphate dehydrogenase (G-6-PD, EC 1.1.1.49) deficiency was performed with dried blood samples on filter paper (Guthrie-cards). Females, known to be heterozygote for G-6-PD deficiency were detected at a rate of approximately 30-70%, depending on the storage conditions of the samples. False positive results in male hemizygotes were eliminated.     

Antioxidant capacity of G-6-PD-deficient erythrocytes

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is the most common human enzymopathy. In this research, we studied two groups consisting of 30 male subjects who are G-6-PD deficient and 30 normal male subjects matched with the G-6-PD-deficient patients for age. All 30 assays were performed under normal conditions free of any oxidative attack that may result in haemolytic crisis in G-6-PD-deficient subjects. The erythrocyte glucose-6-phosphate dehydrogenase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST) activities, reduced glutathione (GSH) levels and erythrocyte and plasma thiobarbituric acid-reactive substances (TBARS) levels were measured. All parameters in each group did not differ significantly except for G-6-PD levels. These data show that G-6-PD-deficient subjects can survive in normal conditions unless they are exposed to any oxidative stress.     

Acetylsalicylic acid-induced hemolysis and its mechanism

Acetylsalicylic acid (ASA) is known to cause severe hemolytic anemia in some glucose-6-phosphate-dehydrogenase-deficient (G-6-PD-deficient) individuals. To study its mechanism, erythrocytes from an ASA-sensitive patient were transfused into a normal compatible recipient. The administration of 2,5-dihydroxybenzoic (gentisic) acid, a known ASA metabolite with redox properties, to the recipient resulted in a marked decrease in the survival of the patient's erythrocytes. Similar studies with red cells from individuals with A- and Mediterranean variants of G-6-PD revealed no alteration in the erythrocytes' survival. Further studies disclosed that both salicylate and gentisate competitively inhibited the G-6-PD from the ASA-sensitive patient resulting in a marked change in the K(m) for NADP. These drugs also inhibited the A- and Mediterranean variants of G-6-PD. The magnitude of inhibition, however, was comparatively small and not different from that observed with a normal enzyme.The above studies suggested that enzyme inhibition by salicylate and gentisate may play an important role in ASA-induced hemolysis. Such an inhibition would further curtail NADPH regeneration, rendering the cells more vulnerable to oxidants. In this connection, gentisate seems to play a major role in ASA-induced hemolysis for it is both a G-6-PD inhibitor and an "oxidant."     

Microheterogeneity of glucose-6-phosphate dehydrogenase phenotypes

Glucose-6-phosphate dehydrogenase (G-6-PD) is the first enzyme of the pentose phosphate pathway and has been extensively investigated. Several variants of G-6-PD were encountered in different regions of Saudi Arabia during an extensive screening programme. A modified rapid isoelectric focussing procedure using LKB Ampholine PAG plates (pH 5.5-8.5) was used to separate the isoenzymes of G-6-PD. G-6-PD-B+ (the normal enzyme) was separated into five major and three minor fractions. The pattern obtained for G-6-PD-A+, G-6-PD-A-, G-6-PD-Mediterranean and G-6-PD-Mediterranean-like showed that the variants differ significantly in their isoenzyme pattern. In this paper it is shown that isoelectric focussing is a sensitive, powerful and reproducible technique to study microheterogeneity of red cell enzymes.     

Decreased survival in vivo of diamide-incubated dog erythrocytes. A model of oxidant-induced hemolysis.

Erythrocytes from patients with chronic hemolytic variants of glucose-6-phosphate dehydrogenase (G-6-PD) deficiency have structural membrane protein abnormalities accompanied by decreased cell membrane deformability which we postulate represent the consequences of oxidant-induced membrane injury. To evaluate the pathophysiologic significance of oxidant-induced membrane injury, we studied the in vitro and in vivo effects of the thiol-oxidizing agent, diamide, on dog erythrocytes. In vitro incubation of dog erythrocytes with 0.4 mM diamide in Tris-buffered saline for 90 min at 37 degrees C resulted in depletion of GSH, formation of membrane polypeptide aggregates (440,000 and > 50,000,000 daltons) and decreased cell micropipette deformability, abnormalities similar to those observed in the erythrocytes of patients with chronic hemolytic variants of G-6-PD deficiency. In addition, diamide-incubated cells had increased viscosity and increased membrane specific gravity, but no change in ATP. Reinjection of 51Cr-labeled, diamide-incubated cells was followed by markedly shortened in vivo survival and splenic sequestration. Further incubation of diamide-incubated cells in 4 mM dithiothreitol reversed the membrane polypeptide aggregates, normalized micropipette deformability, decreased cell viscosity, prolonged in vivi survival, and decreased splenic sequestration. These studied demonstrate that diamide induces a partially reversible erythrocyte lesion which is a useful model of oxidant-induced membrane injury. They suggest that oxidant-induced erythrocyte membrane injury plays an important role in the pathophysiology of chronic hemolysis which accompanies some G-6-PD variants.     

Diagnosis of red cell G-6-PD deficiency in a Chinese neonate

In a neonatal period, a red cell deficiency of glucose-6-phosphate dehydrogenase (G-6-PD) may result in jaundice, the severity of which will vary between patients. Diagnosis of this inborn error of metabolism presents a problem if there is a large number of young enzyme-rich red cells in circulation, and this paper details the technique used to confirm a red cell deficiency of G-6-PD in a neonate.     

四川遂宁地区献血者G-6-PD调查及进食蚕豆对蚕豆病儿输血的影响

应用改良四唑氮兰法对2483名献血者进行红细胞G-6-PD调查,G-6-PD缺乏率为8.3％,其中显著缺乏率为2.1％。建立献血者G-6-PD调查档案,防止蚕豆病儿输入缺乏G-6-PD的血液,提高了输血安全。观察献血者进食蚕豆后不同时间(2～4小时,12～24小时,2～3天)采血对蚕豆病儿输血的影响,各观察组临床症状与外周血Hb的恢复、G-6-PD活性的改变和对照组比较无明显差别,各组均未发现再溶血病例。提示蚕豆病儿在急性溶血后“不应期”内输入进食了蚕豆的献血者的血液无明显不良影响。     

Glucose-6-phosphate dehydrogenase activity in term and near-term, male African American neonates

BACKGROUND: We determined values for glucose-6-phosphate dehydrogenase (G-6-PD) activity in African American neonates. METHODS: G-6-PD activity was measured on umbilical cord blood from term and near-term healthy, male neonates. Neonates were stratified according to the number of neonates for each numerical unit of G-6-PD activity. Corrected end tidal carbon monoxide (ETCOc), a non-invasive index of hemolysis, was performed on each neonate. At least one predischarge transcutaneous bilirubin determination was performed. RESULTS: Five hundred neonates were studied. Two subpopulations were apparent, with no overlap between the subgroups. Mean value for the 64 (12.8%) infants with the lower values (G-6-PD deficient) was 2.7+/-1.1 U/g Hb, range 0.4-6.6 U/g Hb, while that for the 436 neonates with the higher values (G-6-PD normal) was 21.8+/-2.9 U/g Hb, range 14.5-33.8 U/g Hb. No significant differences in activity were noted between those neonates <37 weeks gestational age and those >37 weeks. Enzyme activity in the lower range in both groups was not related to the development of hyperbilirubinemia. G-6-PD enzyme activity did not correlate with ETCOc values either for the entire cohort or for the individual subsets. CONCLUSIONS: G-6-PD-deficient neonates formed a separate subgroup from those with normal enzyme activity. The data supplied should facilitate interpretation of G-6-PD test results.     

Evaluation of glucose-6-phosphate dehydrogenase activity in two different ethnic groups using a kit employing the haemoglobin normalization procedure

AIM: Correct evaluation of Glucose-6-Phosphate Dehydrogenase (G-6-PD) activity of two ethnic groups using a fully quantitative kit with a simultaneous Hemoglobin Normalization (Hb Normalization) procedure. DESIGN AND METHODS: Two groups of mothers and their healthy full term newborns of Greek (n = 1.166) and Albanian (n = 818) origin were tested for their G-6-PD activity employing a direct normalization protocol. RESULTS: Greek mothers and newborns showed a higher prevalence for G-6-PD deficiency as compared to those of Albanian origin. Males of G-6-PD deficient mothers confirmed the efficacy of the method. CONCLUSION: A fully quantitative G-6-PD kit employing Hb Normalization is essential for the correct classification of G-6-PD activity, both in male and female subjects.     

Intravascular hemolysis in aluminium phosphide poisoning.

Intravascular hemolysis is most often secondary to exposure to a variety of drugs or infections, and usually occurs in patients who are deficient in glucose-6-phosphate dehydrogenase (G-6-PD) enzyme. Aluminium phosphide, a fumigant widely used in India, has been reported to produce intravascular hemolysis in only one patient who also had concomitant G-6-PD deficiency. This report describes the occurrence of intravascular hemolysis with aluminium phosphide poisoning in a patient with normal G-6-PD levels. This is of significance as jaundice in patients with this poisoning is often attributed to hepatic damage alone.     

广西地区新生儿疾病筛查结果回顾性分析

目的：了解2009～2012年广西地区新生儿疾病筛查情况及确诊率。方法通过检测促甲状腺素（TSH）筛查甲状腺功能减低症（CH）、苯丙氨酸（PHe）筛查苯丙酮尿症（PKU）、17-羟孕酮（17-OHP）筛查先天性肾上腺皮质增生症（CAH）、葡萄糖-6-磷酸脱氢酶（G-6-PD）筛查G-6-PD缺乏症,对初次筛查阳性的患儿进行及时召回并确诊。结果2009年1月至2012年12月广西新生儿疾病筛查中心合作单位的新生儿筛查率呈逐年上升趋势且CH、PKU、CAH、G-6-PD初次筛查阳性患儿召回率及确诊率存在差异。结论新生儿筛查可以在早期发现CH、PKU、CAH、G-6-PD缺乏症患儿,对其早期进行干预可以防止其发病从而降低对其智力及生长发育的影响,对提高人口素质有重要意义。     

Glucose-6-Phosphate Dehydrogenase (G-6-PD) Hamburg, a New Variant with Chronic Nonspherocytic Haemolytic Anaemia

Abstract. A new variant of G-6-PD with chronic nonspherocytic haemolytic anaemia and very low activity, named G-6-PD Hamburg, was partially purified and biochemically characterized. It was found to have very high lability, an unusually high Km for G-6-P (2000 μM), increased utilization rates for 2-desoxy G-6-P (133%) and galactose-6-phosphate (87%) and an abnormal pH-activity curve. The electrophoretic mobility seemed to be normal. The leukocytes also revealed diminished G-6-PD activity. No impairment of bactericidal activity of neutrophilic granulocytes, as shown by a normal nitroblue tetrazolium reduction, could be demonstrated.     

Lactate dehydrogenase, glucosephosphate dehydrogenase, glutathione reductase and adenosine triphosphatase activities in the erythrocytes of patients with acute viral hepatitis

Some indices of erythrocyte metabolism (EM): activity of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PD), glutathione reductase (GR) and common adenosinetriphosphatase (ATPase) activity were studied in 102 patients with acute viral hepatitis (AVH). The suppression of erythrocyte enzymatic activity (EE) was revealed. It was most noticeable at the peak of average and severe AVH. In a decrease of jaundice and during reconvalescence G-6-PD, GR and ATPase activity reduced up to the control level. The suppression of LDH activity was more noticeable, maintained at discharge and was of prognostic value in investigation at early periods of disease in cases of prolonged reconvalescence. Changes in EE activity showed correlation with indices of liver function (levels of certain bilirubin fractions and transaminase activity). In cases of developing deficiency of erythrocyte G-6-PD activity there was a high correlation between a degree of cytolysis and the suppression of erythrocyte LDH activity. The importance of erythrocyte metabolic derangements revealed in AVH pathogenesis was discussed.     

Glucose-6-phosphate dehydrogenase (G-6-PD) Hamburg, a new variant with chronic nonspherocytic haemolytic anaemia

Abstract. A new variant of G-6-PD with chronic non-spherocytic haemolytic anaemia and very low activity, named G-6-PD Hamburg, was partially purified and biochemically characterized. It was found to have very high lability, an unusually high Km for G-6-P (2000 μM), increased utilization rates for 2-desoxy G-6-P (133%) and galactose-6-phosphate (87%) and an abnormal pH-activity curve. The electrophoretic mobility seemed to be normal. The leukocytes also revealed diminished G-6-PD activity. No impairment of bactericidal activity of neutrophilic granulocytes, as shown by a normal nitroblue tetrazolium reduction, could be demonstrated.     

Studies in hemolysis in glucose-6-phosphate dehydrogenase-deficient African American neonates

BACKGROUND: The role of hemolysis in the mechanism and prediction of hyperbilirubinemia was contrasted between glucose-6-phosphate dehydrogenase (G-6-PD)-deficient and -normal African American neonates. METHODS: Corrected end tidal carbon monoxide (ETCOc) values from the subset of male neonates born to non-smoking African American mothers, drawn from a previously published study, were analyzed. The relationship between ETCOc and bilirubin values, the latter represented as percentiles on the hour of life specific bilirubin nomogram, was determined. Hyperbilirubinemia was defined as any bilirubin value > or =95th percentile for hour of life. RESULTS: 18.6% of 59 G-6-PD-deficient neonates developed hyperbilirubinemia, compared with 7.5% of 362 controls (relative risk 2.50, 95% confidence interval 1.31 to 4.76). As reported, ETCOc values (median, interquartile range) were significantly higher among G-6-PD-deficient neonates than controls (2.4 [2.0-2.9] vs. 2.1 [1.7-2.5] ppm, p<0.001. However, higher ETCOc values were limited to those G-6-PD-deficient neonates with lower bilirubin percentiles: among those whose bilirubin value did not exceed the 95th percentile ETCOc was 2.30 [2.00-2.85] vs. 2.00 [1.70-2.40] ppm in controls, p=0.001. In contrast, among the hyperbilirubinemic neonates ETCOc values were similar between G-6-PD-deficient neonates and controls: 2.7 [2.03-3.33] vs. 2.6 [2.33-3.45] ppm, p=0.9. In the G-6-PD-deficient neonates ETCOc > or =75th percentile contributed no additional predictive value for hyperbilirubinemia (likelihood ratio 1.8). CONCLUSIONS: G-6-PD-deficient African American neonates have increased hemolysis and increased rate of hyperbilirubinemia, but the hemolysis is neither a predominant factor in the pathogenesis of hyperbilirubinemia nor is it predictive of hyperbilirubinemia, over and above the already increased risk conferred by G-6-PD deficiency.