G-6-PD variants: another up-date

G6PDdb, an integrated database of glucose-6-phosphate dehydrogenase (G6PD) mutations

G6PDdb (http://www.rubic.rdg.ac.uk/g6pd/ or http://www.bioinf.org.uk/g6pd/) is a newly created web-accessible locus-specific mutation database for the human Glucose-6-phosphate dehydrogenase (G6PD) gene. The relational database integrates up-to-date mutational and structural data from various databanks (GenBank, Protein Data Bank, etc.) with biochemically characterized variants and their associated phenotypes obtained from published literature and the Favism website. An automated analysis of the mutations likely to have a significant impact on the structure of the protein has been performed using a recently developed procedure. The database may be queried online and the full results of the analysis of the structural impact of mutations are available. The web page provides a form for submitting additional mutation data and is linked to resources such as the Favism website, OMIM, HGMD, HGVBASE, and the PDB. This database provides insights into the molecular aspects and clinical significance of G6PD deficiency for researchers and clinicians and the web page functions as a knowledge base relevant to the understanding of G6PD deficiency and its management.

Molecular characterisation of red cell glucose-6-phosphate dehydrogenase deficiency in Singapore Chinese

Sixty-two G6PD deficient Chinese males have been investigated for the presence of seven mutations of the coding region of the G6PD gene by natural and artificially created amplified restriction sites. The results show that the G to T substitution at nucleotide (nt) 1376 and G to A substitution at nt 1388 represent 24% and 21% of G6PD deficiency, respectively, in the Singapore Chinese; 37% of the sample could not be characterised. The remaining samples were identified as follows: 10% C-->T at nt 563, 5% A-->G at nt 95, and 3% C-->T at nt 1024. The G to A substitution (nt 487) and the substitution A-->G (nt 493) were not present in this sample. None of the subjects with the Mediterranean mutation (563 C-->T) had the silent mutation at 1311 (C-->T). This study confirms the extreme molecular heterogeneity of the G6PD gene in the Chinese.

Study of glucose-6-phosphate dehydrogenase: history and molecular biology

Glucose-6-phosphate dehydrogenase (G6PD) deficiency was discovered in the 1950s. The history of the development of knowledge about G6PD deficiency is reviewed here. In the first decade after its discovery, the clinical manifestations of G6PD deficiency began to be understood. In the second decade, attention was focused on the degree of variability of this enzyme and the distinction of the various biochemical variants from one another. In the last decade, it has been possible to understand the mutations that effect this enzyme at the DNA level. Some 40 different mutations have now been characterized. Analysis of these mutations indicates that, while diversity sometimes exists within a mutation considered biochemical homogeneous, more often variants thought to be distinct prove to be identical. The study of G6PD mutations is beginning to provide insight into structure-function relationships.

X-linked glucose-6-phosphate dehydrogenase (G6PD) and autosomal 6-phosphogluconate dehydrogenase (6PGD) polymorphisms in baboons

Electrophoretic polymorphisms of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) were examined in captive colonies of five subspecies of baboons (Papio hamadryas). Phenotype frequencies and family data verified the X-linked inheritance of the G6PD polymorphism. Insufficient family data were available to confirm autosomal inheritance of the 6PGD polymorphism, but the electrophoretic patterns of variant types (putative heterozygotes) suggested the codominant expression of alleles at an autosomal locus. Implications of the G6PD polymorphism are discussed with regard to its utility as a marker system for research on X-chromosome inactivation during baboon development and for studies of clonal cell proliferation and/or cell selection during the development of atherosclerotic lesions in the baboon model.

Biochemical characteristics of glucose-6-phosphate dehydrogenase variants among the Malays of Singapore with report of a new non-deficient (GdSingapore) and three deficient variants

Biochemical characteristics of one non-deficient fast G6PD variant (GdSingapore) and six different deficient variants (three new, two Mahidol, one each of Indonesian and Mediterranean) were studied among the Malays of Singapore. The GdSingapore variant had normal enzyme activity (82%) and fast electrophoretic mobilities (140% in TEB buffer, 160% in phosphate and 140% in Tris-HCl buffer systems respectively). This variant is further characterized by normal Km for G6P; utilization of analogues (Gal6P, 2dG6P; dAmNADP), heat stability and pH optimum. The other six deficient G6PD variants had normal electrophoretic mobility in TEB buffer with enzyme activities ranging from 1 to 12% of GdB+. The biochemical characteristics identity them to be 2 Mahidol, 1 Indonesian and 1 Mediterranean variants and three new deficient variants.

Characterization of a new G6PD variant: G6PD Titusville

We describe a new glucose-6-phosphate dehydrogenase mutant, G-6-PD Titusville. The propositus is a 7-month-old black male infant with a transient hemolytic episode. The mutant enzyme is characterized by abnormal electrophoretic mobility, thermolability, Km for NADP, abnormal deamino NADP use and a decreased sensitivity to inhibition by NADPH. G-6-PD activity of hemolysate, as measured under optimal in vitro conditions, was not initially decreased, whereas fibroblasts, granulocytes, and platelets showed a markedly decreased level of enzyme activity. These properties identify G6PD Titusville as a unique variant of this X-linked, housekeeping enzyme. We conclude that although the propositus with G6PD Titusville had a transient hemolytic episode, we cannot be certain whether this association was a causative one.

G6PD Avenches and G6PD Moosburg: biochemical and erythrocyte membrane characterization

Two new G6PD variants with severe enzyme deficiency in Switzerland (G6PD Avenches, G6PD I) and in Germany (G6PD Moosburg, G6PD II) are described. One patient had suffered from severe postpartal hyperbilirubinemia, the other one presented with chronic hemolysis and remittent hyperbilirubinemia. Both variants showed diminished electrophoretic mobility, both variants were heat labile. The Michaelis-Menten constants KM for glucose-6-phosphate and for NADP+ were normal. 2-Desoxy-glucose-6-phosphate was utilized by G6PD I in a higher and by G6PD II at a lower rate than by the normal enzyme. Desamino-NADP+ and galactose-6-phosphate were utilized by both variants at a normal rate. The electrophoretic separation of membrane proteins of G6PD II showed both in the presence and in the absence of 6-mercaptoethanol no difference concerning the formation of membrane protein aggregates between patient and normal control.

Glucose-6-phosphate dehydrogenase variants and their frequency in Guangdong, China

Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) was characterized in blood samples obtained from 97 randomly selected males with enzyme deficiency from various regions of Guangdong Province, China. Nine new variants (Gd Kaiping, Gd Boluo, Gd Huiyang, Gd Gaomin, Gd Qing-Baijiang, Gd Gaozhou, Gd Huazhou, Gd Nanhai, and Gd Guangzhou) were identified. Of the 31 variants found in this province, Gd Kaiping, Gd Taiwan-Hakka, Gd Haad Yai, Gd Haad Yai-like and Gd Huiyang occurred most frequently. The frequency of each variant was calculated. The results demonstrated that the genetic heterogeneity of G6PD deficiency was high in this area.

G6PD Huntsville: a new glucose-6-phosphate dehydrogenase associated with chronic hemolytic anemia

We describe a previously unreported glucose-6-phosphate dehydrogenase (G6PD) variant. G6PD Huntsville was found in a Caucasian male, resident of Huntsville, Alabama who was investigated for otherwise unexplained chronic hemolytic anemia. An unusual feature of this unique, apparently hemolytic, G6PD mutant is that its red cell enzymatic activity has not been decreased. The mutant enzyme is unstable. Additionally, the enzyme variant is characterized by normal electrophoretic mobility, biphasic and slightly alkaline pH optimum, and abnormal kinetics for the natural substrates G6PD and NADP as well as the artificial substrates deamino NADP. Its activity for another artificial substrate 2-deoxy G6PD is normal. The inhibition constant for NADPH is normal. The subject has had no evidence of episodic jaundice.

Characterization of a new glucose-6-phosphate dehydrogenase variant: G6PD Central City

Glucose-6-phosphate-dehydrogenase deficiency is the most common disease-producing enzyme deficiency in man. This paper describes a new glucose-6-phosphate-dehydrogenase variant discovered during the evaluation of an episode of acute hemolytic anemia in a 62-year-old black male, which was temporally related to the ingestion of Tolbutamide. The hemolysis resolved within 10 days despite continuation of Tolbutamide. The erythrocyte glucose-6-phosphate-dehydrogenase activity was significantly decreased, and its electrophoretic mobility was indistinguishable from wild type enzyme, though faster on starch gel with tris, borate, and phosphate buffers. The enzyme had a biphasic pH optimum reduced Km for G-6-P and NADP, decreased utilization of deamino-NADP, and reduced Ki for NADPH. Because the kinetic properties of this enzyme were unique, we have designated it as G6PD Central City.

A new glucose-6-phosphate dehydrogenase variant (G6PD Tsukui) associated with congenital hemolytic anemia

A new glucose-6-phosphate dehydrogenase (G6PD) variant associated with chronic nonspherocytic hemolytic anemia was found in a 20-year-old Japanese male who showed mild hemolysis after an upper respiratory tract infection. The patient had been noted to have jaundice and reticulocytosis several times before this episode. The enzyme activity of the variant was 1.5% of normal. The enzymatic characteristics were slow anodal electrophoretic mobility, high Km G6P, normal Km NADP, decreased heat stability, and a normal pH optimum. From these results, the enzyme was considered to be a new class 1 variant and was designated G6PD Tsukui.

Two apparent glucose-6-phosphate dehydrogenase variants in normal XY males: G6PD Alabama

A six-year-old black boy who had transient hemolysis after a viral infection was found to have mildly decreased red cell glucose-6-phosphate dehydrogenase (G6PD) activity (1.25 IU/g hemoglobin). Two G6PD bands, both slightly faster than normal G6PD B, were seen on electrophoresis in both the propositus as well as in his maternal grandfather. This is an unexpected finding, since the G6PD gene is located on the long arm of the X chromosome that is subject to X-chromosome inactivation, and available evidence indicates that it is present as a single functional copy in the human genome. The obvious possibility of duplication of the X chromosome was eliminated by cytogenetic analysis with G-banding. G6PD duplication is unlikely, since peripheral blood granulocytes, platelets, and lymphocytes; cultured skin and bone marrow fibroblasts; and Epstein-Barr virus-stimulated lymphocytes yielded only a single electrophoretic band with mobility identical to the slower band seen in crude red blood cell hemolysate. Study of partially purified red blood cell hemolysate G6PD also yielded a single band with identical mobility. Kinetic studies of the enzyme in the propositus and in three generations of his family identified a unique, previously unpublished G6PD mutant that is herein designated G6PD Alabama. Red blood cells were separated by density gradient into a reticulocyte-enriched, an intermediate, and a dense, older portion. Two distinct enzyme bands were identified on electrophoresis of hemolysate from the reticulocyte-enriched portion, but not from the other two portions. It is postulated that two transcriptional products of the mutant G6PD gene exist; one with a short half-life and detectable only in young red blood cells, and another with a longer half-life present in all cells. The existence of two distinct mutant genes in the genome or a unique post-translational form of the mutant G6PD detected only in reticulocytes cannot be excluded.

Gd(+)Cuiabá, a new rare glucose-6-phosphate dehydrogenase variant presenting normal activity

A 33-year-old Brazilian male of Portuguese extraction was found to have a new glucose-6-phosphate dehydrogenase variant, herein named Gd(+)Cuiabá. The enzyme variant is characterized by normal activity, normal electrophoretic mobility, high Km for glucose-6-phosphate, high Ki for NADPH, decreased thermal stability, normal utilization of substrate analogues and normal pH curve.

Glucose-6-phosphate dehydrogenase (G6PD) Guantánamo and G6PD Caujerí: two new glucose-6-phosphate dehydrogenase-deficient variants found in Cuba

Glucose-6-phosphate dehydrogenase (G6PD) deficiency was identified in two children who were studied because of hemolytic episodes. The electrophoretic and kinetic properties of the mutant enzymes allowed us to conclude that both of them were new variants. They were named G6PD Guantánamo and G6PD Caujerí.

Distribution of Gd- alleles in some ethnic groups of the USSR

A population study of Gd- allele distribution was made in similar (age-sex) samples of schoolchildren and students from different ethnic groups: Russians, Ashkenazi Jews, and Azerbaijanians. Both the frequency and the spectrum of the Gd- alleles were quite different. The Gd- frequency in Russians (Kostroma region) was 0.36%; in Ashkenazim (Gomel region), 0.91%; in Azerbaijanians (Sheki region and Apsheron region), 3.6% and 10.5%, respectively. G6PD deficiency in Russians is represented by familial forms; in Ashkenazi Jews by class II alleles Kirovograd and Zhitomir; and in Azerbaijanians, by a wide spectrum of class II and III alleles. Genetic factors involved in the formation of Gd- allele frequencies and the spectrum in these three ethnic groups are discussed.

G-6-PD Jalisco and G-6-PD Morelia: two new Mexican variants

Two new G-6-PD variants designated G-6-PD Jalisco and G-6-PD Morelia were identified in two unrelated Mexican families. An additional G-6-PD variant was found in each family: G-6-PD Trinacria and G-6-PD A-. In both families compound heterozygotes were identified. G-6-PD Jalisco and G-6-PD Morelia belong to Classes 3 and 4, respectively. G-6-PD Morelia is the first variant from its class with a high Km for NADP and a low Ki for NADPH.

Electrophoretic variants of blood proteins in Japanese. IV. Prevalence and enzymologic characteristics of glucose-6-phosphate dehydrogenase variants in Hiroshima and Nagasaki

Electrophoretic screening of glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6PD) was conducted one sample of 9,260 children born to the atomic bomb survivors in Hiroshima (Honshu) and Nagasaki (Kyushu). The prevalence of electrophoretic variants was 0.11% in males and 0.42% in females in Hiroshima, and 0.16% in males and 0.31% in females in Nagasaki. Enzymologic characteristics of 10 variants obtained from three males and seven hemizygous fathers of heterozygous females were examined. As a result, three new types of G6PD variants were identified among five variants detected in Hiroshima, and three new types among five variants in Nagasaki. All the variants except one belonged to Class 3, as defined by Yoshida et al. (1971).

Genetic heterogeneity at the glucose-6-phosphate dehydrogenase locus in southern Italy: a study on the population of Naples

Glucose-6-phosphate dehydrogenase (G6PD) electrophoretic phenotype was determined in red cells from 979 male subjects born in Naples (Southern Italy). In 0.7% of the cases no activity could be detected in haemolysates, while in 1.3% of the cases G6PD activity was approximately 20% of normal and electrophoretic mobility was altered. Moreover in two subjects a G6PD with altered mobility and normal activity was shown. G6PD was characterized in 10 subjects with variant phenotype. We conclude that the G6PD(-) phenotype in the population of Naples consists of at least six different G6PD variants associated with mild deficiency and at least one, G6PD Mediterranean, associated with severe deficiency.

Genetic variants of human erythrocyte glucose-6-phosphate dehydrogenase: new characterization data obtained by multivariate analysis

Thirteen variables used in the course of characterization of G6PD variants from forty-one individuals have been submitted to multivariate factorial and cluster analysis. Because of the diagrammatic representation of the analysis, two main findings were made possible. Firstly, the three-dimensional plot of the experimental data gives the advantage of a model of classification which is closely related to the ethnogeographical origin of the subjects, and to the clinical and haematological incidence of the G6PD variants. Secondly, cluster analysis visualizes the distance between the G6PDs examined. In this respect, it was determined that three local original variants associated with acute haemolytic anaemia showed a close relationship and belonged to the same cluster (Gd(-) Toulouse, Gd(-) Muret and Gd(-) Colomiers). Conversely, two non-haemolytic variants (G6PD Luz Saint Sauveur and Lozère) were found to be linked in another remote cluster. The procedure developed in this work promotes a new approach to G6PD characteristics in human genetic studies.

Glucose-6-phosphate dehydrogenase. A transferred nuclear Overhauser enhancement study of NADP+ conformations in enzyme-coenzyme binary complexes

The conformation of NADP+ in glucose-6-phosphate-dehydrogenase--NADP+ binary complexes has been investigated using proton-proton transferred nuclear Overhauser enhancement measurements to determine interproton distance ratios between bound NADP+ protons. The enzymes from Saccharomyces cerevisiae (brewer's yeast and baker's yeast) and Hansenula jadinii (Candida utilis, Torula utilis) form binary complexes with NADP+ in which the glycosidic bond of the adenine moiety is in the anti conformation whereas that of the nicotinamide moiety exists as a syn (69-70%)/anti (30-40%) mixture. The enzymes have similar subunit sizes (Mr approximately 58 000) and it is shown that they bind NADP+ in essentially similar conformations. Inactivation of the baker's yeast enzyme with acetylsalicylic acid caused little if any alteration in the conformation of bound NADP+, and the presence of NADP+ during inactivation afforded very little protection to the enzyme. Inactivation rates were, however, lower in the presence of glucose 6-phosphate. It is concluded that the epsilon-amino group of the lysine residue that is acetylated during the inactivation reaction with acetylsalicylic acid is not necessary for binary complex formation between the enzyme and NADP+, but that it is situated in a part of the molecule affected by formation of the enzyme--glucose-6-phosphate complex. The implication of the findings for the catalytic process, and related evolutionary aspects, are discussed briefly.

A unique electrophoretic slow-moving glucose 6-phosphate dehydrogenase variant (G6PD Asahikawa) with a markedly acidic pH optimum

A new glucose 6-phosphate dehydrogenase (G6PD) variant associated with chronic nonspherocytic hemolytic anemia was discovered in Japan. The patient showed hemolytic crises after upper respiratory infections. The enzyme activity was about 3.8% of the normal. The partially purified enzyme revealed slow anodal electrophoretic mobility, high Km NADP, marked thermal-instability, and increased affinity for a substrate analogue (deamino-NADP). A particular characteristic of this enzyme was a biphasic pH curve with a greatly increased activity at low pH values. From these results, this variant was clearly different from hitherto observed G6PD variants, and was designated G6PD Asahikawa.

Genetic polymorphism of G6PD in a Bulgarian population

Considerable genetic heterogeneity in G6PD was found in the Bulgarian population-14 G6PD variants isolated from 117 hemizygous carriers of G6PD deficiency. Of these, G6PD Mediterranean type was a polymorphic variant and G6PD Corinth occurred with high frequency. Two new variants were identified-G6PD Rudosem and G6PD Nedelino. In a selected group of 78 subjects with clinical manifestations, four variants were established: G6PD Mediterranian, G6PD Corinth, G6PD Seattle and G6PD Ohut II.

Gd(-) Gifu and Gd(-) Fukuoka. Two new variants of glucose-6-phosphate dehydrogenase found in Japan

Two new glucose-6-phosphate dehydrogenase (G6PD) variants were discovered in Japan. The first, found in a 9-year-old male, was associated with chronic hemolysis and hemolytic crises after upper respiratory infections. The enzyme activity of the variant was 2.9% of normal. The patient's G6PD showed an increased utilization of substrate analogue, deamino-NADP, and thermal instability. The second variant occurred in a 7-year-old male with drug-induced hemolysis. The main enzymatic characteristics were reduced enzyme activity, being 6.4% of normal, faster-than-normal anodal electrophoretic mobility, slightly high Michaelis constant for glucose-6-phosphate, thermal instability, and biphasic pH optima. Enzymatic properties of these variants allowed each to be distinguished from previously reported variants. The first variant was designated Gd(-)Gifu and the other, Gd(-)Fukuoka.

G6PD Cagliari: a new low activity glucose 6-phosphate dehydrogenase variant characterized by enhanced intracellular lability

A new variant of human erythrocyte glucose 6-phosphate dehydrogenase (G6PD), designated G6PD Cagliari, has been characterized. It is associated with severe enzyme deficiency and can be placed in Class 2 of the usual tabulation of G6PD variants. The specific activity of this variant is near normal, while its decay within the circulating erythrocytes is very rapid compared with normals. Genetic analysis of the family of the propositus indicated that the two available females are heterozygotes characterized by extremely unbalanced mosaic phenotypes.

Gd (+) Laguna, a new rare glucose-6-phosphate dehydrogenase variant from Brazil

A new G6PD variant, designated Gd (+) Laguna, was found in a 9-year-old Brazilian boy of Portuguese ancestry suffering from an iron-refractory anemia. The red cell enzyme activity of the subject was 64%. The mutant enzyme showed slower electrophoretic mobility, increased affinity for glucose-6-phosphate, decreased affinity for NADP+, elevated utilization of substrate analogues, decreased inhibition of NADPH, normal heat stability and a biphasic pH curve. The occurrence of the variant in two non-anemic relatives of the propositus indicates that the association between this G6PD type and anemia may be coincidental.

Red cell metabolism: a comparative study of some mammalian species

The activities of six enzymes--glucose-6-phosphate dehydrogenase (G-6-PD), 6-phosphogluconate dehydrogenase (6-PGD), glutathione reductase (GR), glutathione peroxidase (GSH-Px), catalase and superoxide dismutase (SOD)--and levels of reduced glutathione (GSH) and GSH regeneration rates were measured in the red blood cells of eight mammalian species--rabbit, guinea-pig, rat, golden hamster, sheep, goat, cattle and human. The results show that whereas the activities of G-6-PD, 6-PGD and GR are widely different among the experimental animals, there is no such variation in the activity of SOD. There does not appear to be a relationship between GSH regeneration rate and the activities of G-6-PD, 6-PGD and GR--the enzymes associated with GSH metabolism.