Enzyme kinetics and molecular modeling studies of G6PDMahidol associated with acute hemolytic anemia.

G6PDMahidol enzyme is the most common variant in the Achang Chinese ethnic group and clinically manifests as class II. In this study, G6PDMahidol enzyme was characterized by molecular modeling to understand its kinetics. G6PDMahidol, G6PDG487A and G6PDWT proteins were heterologously expressed in the G6PD-deficient DF213 E. coli strain, purified and their steady-state kinetic parameters were determined. Compared with G6PDWT, the Km and Vmax of NADP+ with G6PDG487A were about 28-fold and 12-fold lower, respectively. The Ki values of dehydroepiandrosterone (DHEA), NADPH and ATP with G6PDG487A showed 29.5-fold, 2.36-fold reduction and 1.83-fold increase, respectively. A molecular modeling of G6PDG487A was performed based on the X-ray structure of human G6PD (PDB: 2BH9). It is suggested that Ser-163 might affect the stability of G6PDG487A -helix d and -strand E, besides the conformation of -strand D. In conclusion, the biochemical and structural properties of G6PDG487A and G6PDWT enzymes are significantly different, which may be responsible for clinical diversity of G6PD deficiencies.

Molecular basis of G6PD deficiency: Current status and its perspective

Glucose-6-phosphate dehydrogenase is an essential enzyme to cell growth. Its deficiency of enzyme plays an important role in senescence and death signaling. Also, it is actually the most common clinically important enzyme defect, not only in hematology, but also among all human known diseases. Clinical consequences of enzyme deficiency are: neonatal hyperbilirubinemia, acute hemolytic anemia, and chronic hemolytic anemia. The enzyme gene spans 18 kb on the X chromosome [xq28] and contains 13 exons. Its promoter is embedded in a CpG island that is conserved from mice to humans. The development of a number of PCR-based methods for the detection of known mutations in Glucose- 6-phosphate dehydrogenase has made it possible to detect enzyme deficiency and identify the specific mutation responsible with relative ease. We will discuss the mentioned clinical manifestations of glucose-6-phosphate dehydrogenase deficiency, Genetics, biochemistry and pathophysiology of the enzyme in details using newer published data and present most of the studies in Iranian population

Glucose-6-phosphate dehydrogenase activity in Jordanian female children with acute hemolytic crises

The study objective is to determine the mode of inheritance in Glucose-6-Phosphate Dehydrogenase [G6PD]-deficient female children who have a history of acute hemolytic crises. Also, it aims to study the relationship between the type of inheritance and the severity of hemolysis, and to determine the factors incriminated in provoking hemolytic crises on them. The study included 40 female children with confirmed diagnosis of G6PD deficiency who were admitted to Princess Rahma Teaching Hospital with acute hemolytic crisis between June 2002 and April 2005. G6PD enzyme levels were studied in their mothers and in thirty-seven fathers to determine the mode of inheritance. In addition, 45 unaffected volunteers were evaluated as a control group. The results showed that 65% were heterozygous females and 35% were homozygous for G6PD deficiency. The mean G6PD level for homozygous females was 4.79 +/- 2.67 mU/10[9] RBCs compared to 54.1 +/- 23.2 mU/10[9] RBCs in heterozygous females. In 92.5% of children there was a history of fava beans ingestion before crisis. The mean time for appearance of symptoms after ingestion of fava beans was 10.57 +/- 4.99 hours compared to 23.77 +/- 5.23 hours in heterozygous females, and the duration of hemolytic crises was higher in homozygous females: 78 +/- 12.2 hours compared to 53 +/- 10 hours in heterozygous females. Two breast-feed infants gave history of fava beans ingestion by their mothers before crisis. This study demonstrated that females with G6PD activity level of less than 10% are usually homozygous females with rapid onset of symptoms and longer duration of hemolytic crisis following exposure to triggering factors, especially uncooked green beans, whose metabolites may be excreted in breast milk

Dos nuevas mutaciones de glucosa 6 fosfato deshidrogenasa, G6PD Santiago y G6PD Calvo Mackenna / Two new glucose 6 phosphate dehydrogenase mutations, G6PD Santiago and G6PD Calvo Mackenna

Se describen dos nuevas mutaciones que producen deficiencia de G6PD, ambas en niños chilenos con anemia hemolíticas crónica no esferocítica (AHCNE). La mutación G6PD Santiago es debida a un cambio de arginina a prolina en el aminoácido 198, lo que lleva a una sustitución de guanina por citosina en el nucleótido 593 del exon 6. En la mutación G6PD Calvo Mackenna hay un cambio de valina a isoleucina en el aminoácido 380, lo que produce una sustitución de adenina por guanina en el nucleotido 1138 del exon 10 de la enzima. Los estudios para el diagnóstico de ellas se realizaron en "The Scripps and Research Institute de La Jolla, California, USA" por gentileza del Dr Ernest Beutler

Glicose-6-fosfato desidrogenase: aspectos clínicos / Glucose-6-phosphate dehydrogenases: clinical aspects

In this article, the authors presente a review about the behaviour of G6PD in relation to pathologies other than hemolytic anemias, which are the many diagnostic use of the enzyme

Anemias hemolíticas: enzimopatias / Hemolytic anemias: enzimopaties

O estudo das alterações bioquímicas dos eritrócitos pode explicar uma variedade de anemias hemolíticas, pois, como se sabe, as hemácias são células bem diferenciadas do organismo. A hemácia madura metabolicamente, funciona quase que exclusivamente por glicólise. O estudo do fluxo glicolítico em hemácias humanas, pode detectar e explicar algumas anemias através de determinações hematológicas e bioquímicas. Através de avaliação cuidadosa é possível se determinar a exata deficiência bioquímica responsável pelas anemias hemolíticas a exemplo daquelas onde ocorre o envolvimento da hexoquinase, da fosfofrutoquinase, da piruvatoquinase, da gliceraldeído-3-fosfato desidrogenase, da enolase e da glicose-6-fosfato desidrogenase. Esta avaliação orienta os pacientes portadores desta patologia no sentido de terem condições de evitar as crises hemolíticas a que possam estar sujeitos, o que facilitará sobremaneira as intervenções medicamentosas e cirúrgicas

Las eritroenzimopatías hereditarias. I. Aspectos bioquímicos y genéticos / Hereditary red blood cell enzyme disorders. I. Biochemical and genetic aspects

Se presenta una revisión general de las anemias hemolíticas hereditarias por defectos enzimaticos en el metabolismo del eritrócito y de la asociación de estos defectos con icterícia neonatal