ABSTRACT
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.
Subject(s)
Acute Disease , Adolescent , Anemia, Hemolytic/enzymology , Anemia, Hemolytic/etiology , Asian People , Computer Simulation , Female , Glucosephosphate Dehydrogenase/antagonists & inhibitors , Glucosephosphate Dehydrogenase/chemistry , Glucosephosphate Dehydrogenase/pharmacokinetics , Glucosephosphate Dehydrogenase Deficiency/complications , Glucosephosphate Dehydrogenase Deficiency/enzymology , Humans , Kinetics , Molecular Dynamics Simulation , MutationABSTRACT
To study the mechanism of haemolysis in G6PD deficient erythrocytes, studies were undertaken in G6PD deficiency and in normal erythrocytes artificially loaded with calcium. Significantly increased concentrations of calcium, calcium activated neutral protease (CANP) and calcium ATPase were found in patients of G6PD deficiency. However, the membrane bound calcium, the total glycoprotein and sulphydryl groups of membrane were observed to be decreased. Similar results were also observed in the normal erythrocytes when loaded with calcium. These results point to the role of the proteolytic process in membrane modification, and altered membrane permeability during the haemolytic process. Our observations in G6PD deficiency and in in vitro point to the existence of a calcium dependent proteolytic preconditioning of erythrocyte accelerating the haemolysis.
Subject(s)
Adult , Calcium/pharmacology , Calcium-Transporting ATPases/drug effects , Child , Child, Preschool , Endopeptidases/drug effects , Enzyme Activation , Female , Glucosephosphate Dehydrogenase Deficiency/enzymology , Humans , Infant , Male , MutationABSTRACT
It seems that thalassemia and/or hemoglobinopathies and glucose-6-phosphate dehydrogenase deficiency (G-6-PD) have some protective effects against malaria infection. To verify this, hemoglobin typing and methehoglobin reduction test were performed on 115 malaria patients and compared with controls. It was found that the number of thalassemia/hemoglobinopathies in the malaria group and in the control group were not significantly different and also occurrence of G-6-PD deficiency in the malaria group was not different from that of the controls. Clinical manifestations of malaria in any group are quite similar. It is concluded that there is no protective effect against malaria in thalassemia/hemoglobinopathies or G-6-PD deficiency.
Subject(s)
Adolescent , Adult , Aged , Cross-Sectional Studies , Developing Countries , Erythrocytes/enzymology , Female , Glucosephosphate Dehydrogenase/blood , Glucosephosphate Dehydrogenase Deficiency/enzymology , Hemoglobinopathies/enzymology , Humans , Incidence , Malaria/enzymology , Male , Middle Aged , Risk Factors , Thailand/epidemiology , Thalassemia/enzymologyABSTRACT
A new Indian G6PD variant was detected in a 15 yr old Maratha male during a population screening programme in high school children in Bombay (India). The propositus and two family members having the same variant were apparently healthy. This enzyme variant has a mild erythrocyte G6PD deficiency and a slow electrophoretic mobility. It is characterized by a high Michaelis-Menton constant for G6P, a bimodal curve for pH optima and a slight decrease in the thermostability. The rate of utilization of substrate analogue is similar to that of normal. These observations suggest identification of a new class III variant, designated as G6PD Rohini.
Subject(s)
Adolescent , Adult , Child , Electrophoresis, Starch Gel , Erythrocytes/enzymology , Genetic Variation , Glucosephosphate Dehydrogenase/genetics , Glucosephosphate Dehydrogenase Deficiency/enzymology , Humans , India , Male , Mass Screening , PedigreeABSTRACT
A 27 year old Brazilian male of both Portuguese and Spanish origin presenting nonspherocytic chronic hemolytic anemia was found to have a rare glucose-6-phosphate dehydrogenase variant herein named Gd(-) Carapicuiba. The red blood cell enzyme variant is characterized by a moderate enzyme deficiency (47%), high Km for its substrates G6P and NADP, decreased activity against deamino-NADP, increased Ki for NADPH and decreased heat stability. The clinical signs of the patient are probably related to these properties of the enzyme variant
Subject(s)
Adult , Humans , Male , Anemia, Hemolytic, Congenital Nonspherocytic/enzymology , Erythrocytes/enzymology , Glucosephosphate Dehydrogenase Deficiency/enzymology , Glucosephosphate Dehydrogenase/genetics , Anemia, Hemolytic, Congenital Nonspherocytic/complications , Genetic Variation , Glucosephosphate Dehydrogenase Deficiency/complications , Glucosephosphate Dehydrogenase/blood , Hemolysis , PedigreeSubject(s)
Adolescent , Adult , Child , Female , Glucosephosphate Dehydrogenase Deficiency/enzymology , Humans , India , MaleABSTRACT
Partial purified erythrocyte G-6-PD from 25 G-6-PD deficient southern Chinese male residents in Thailand was characterized. Five G-6-PD variants were found : G-6-PDs Canton (8), Dhon (or Taipei-Hakka) (8), Mahidol (or B (-) Chinese) (6), Haad Yai (1), and Hong Kong (1). One person whose enzyme was not fully characterized might have G-6-PD Haad Yai or a new variant.