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Chronic non-spherocytic haemolytic disorders associated with glucose-6-phosphate dehydrogenase variants
G Fiorelli1, F Martinez di Montemuros, M D Cappellini
1Department of Internal Medicine, University of Milan, Italy.
Insights
Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzyme defect, can cause chronic hemolytic anemia. Class I G6PD variants often show reduced enzyme stability and altered kinetic properties, contributing to this condition.
Area of Science:
- Biochemistry
- Genetics
- Hematology
Background:
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most prevalent human enzyme defect, affecting over 400 million individuals globally.
- Certain G6PD variants can lead to chronic hemolytic anemia (CNSHA), particularly under oxidative stress.
Purpose of the Study:
- To review and analyze the characteristics of 61 identified G6PD molecular variants associated with CNSHA.
- To identify common biochemical and stability properties among Class I G6PD variants causing severe red blood cell enzyme instability.
Main Methods:
- Revisiting and analyzing data from 61 previously described Class I G6PD variants.
- Examining enzyme kinetics (Ki for NADPH, Km for substrates) and thermostability.
Main Results:
- A significant number of Class I G6PD variants exhibit reduced red blood cell enzyme stability.
- Common characteristics include a low inhibition constant (Ki) for NADPH, a higher Michaelis constant (Km) for substrates, and reduced thermostability.
Conclusions:
- Class I G6PD variants share common biochemical and stability defects that contribute to chronic non-spherocytic hemolytic anemia.
- Understanding these variant properties is crucial for diagnosing and managing G6PD deficiency-related hemolytic conditions.
Abstract:
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect, being present in over 400 million people world wide. In a small number of cases, G6PD deficiency can lead to mild-to-severe chronic haemolysis, which is further exacerbated by oxidative stress. Such G6PD variants have been described all over the world and are responsible for chronic non-spherocytic haemolytic anaemia (CNSHA). To date 61 G6PD molecular variants associated with CNSHA have been identified, only some of which can cause the severe reduction in stability of the red blood cell enzyme. The distribution of the different mutations shows a predominance of small mutational events, and many have been found repeatedly in different parts of the world. By revisiting the 61 class I variants described so far, we can observe that a low inhibition constant (Ki) for NADPH, a higher Km for substrates and a reduced thermostability are common.