G6PD Deficiency

 G6PD - Glucose-6-Phosphate-Dehydrogenase

Glucose-6-Phosphate-Dehydrogenase Deficiency (G-6-PD) is a genetic deficiency that causes red blood cells to hemolyze in the presence of certain drugs or chemicals, infections or other stressors.

The deficiency is statistically determined to affect more than four hundred million people globally, mostly people of African and Middle Eastern descent.

When triggered, symptoms include fever, dark colored urine, abdominal and back pain, fatigue, and pale skin.

A trigger is any chemical (from food, drugs etc), disease condition, stress or other environmental factor that could start oxidative stress in the red blood cells. The absence of G6PD enzymes or insufficiency of the enzymes to repel the oxidation. The result is hemolysis which is early death of the red blood cells. When enough red blood cells have died, anemia sets. If anemia continues to grow and the course is not reversed, the symptoms identified above may begin to show up and in time, really bad things happen like organ damage and organ failure and death.

G-6-PD (also G6PD) deficiency is a result of G6PD gene mutation.

The gene provides instructions for making an enzyme called glucose-6-phosphate dehydrogenase.

The enzyme (aka as G6PDH) is a cytosolic enzyme that catalyzes the chemical reaction


D-glucose 6-phosphate + NA dP+<----> 6-phosphate-D-glucano-1,5-lactone + NA dP H + H+


G6PD sites labeled.png

The enzyme participates in the pentose phosphate pathway, which is a metabolic pathway that supplies

reducing energy to cells, such a erythrocytes, by maintaining the levels of the coenzyme nicotinamide

adenine dinucleotide phosphate (NADPH).


The NADPH the maintains the level of glutathione in these cells that help protect the red blood cells

against oxidative damage from compounds like hydrogen peroxide. 


The G6PDH enzyme is active in virtually all cell types and is involved in the normal processing of

carbohydrates. It plays a critical role in red blood cells as described above. It helps protect red blood

from premature destruction (hemolysis). It is responsible for the first step in the pentose phosphate

pathway, a series of chemical reactions that convert glucose to another sugar, ribose-5-phosphate.


Ribose-5-phosphate is an important component of nucleotides, which are the building blocks of DNA and

it’s chemical cousin RNA. The chemical reaction produces NADPH as shown above, which plays a role

in protecting cells from potentially harmful molecules called reactive oxygen species.


These molecules are by products of normal cellular functions. Reactions involving NADPH produces

compounds that prevent reactive oxygen species from building up to toxic levels within cells.

The production of NADPH by G6PD is essential in red blood cells, which are particularly susceptible

to damage by reactive oxygen species because they lack other NADPH-producing enzymes.


More than 200 mutations that causes glucose-6-phosphate dehydrogenase deficiency have been

identified in the G6PD gene. Almost all these mutations lead to changes in single building blocks

(amino acids) in the glucose-6-phosphate dehydrogenase enzyme.


These changes disrupt normal structure and functions of the enzyme or reduce the amount of the enzyme

produced in cells.


Cytogenetic Location: Xq28, which is the long (q) arm of the X chromosome at position 28

The gene is in the X chromosome. The deficiency is more common among men. It is located in Xq28as

shown above. The G6PD deficiency may cause neonatal jaundice, acute hemolysis, or severe and chronic

non-spherocytic hemolytic anemia. In rare cases, it may result in acute renal failure.


Without enough functional glucose-6-phosphate dehydrogenase, red blood cells are unable to

protect themselves from the damaging effects of reactive species.


The damaged cells are likely to rupture and break down prematurely (undergoing hemolysis).

Factors such as infections, certain drugs, and ingesting fava beans can increase the levels of reactive

oxygen species, causing red blood cells to hemolyze faster than they can be replaced by the body.


Primary symptom of this condition is hemolytic anemia.


References:


 Wikipedia : https://en.wikipedia.org/wiki/Glucose-6-phosphate_dehydrogenase

 NIH gene site: https://ghr.nlm.nih.gov/gene/G6PD#resources

 G6PD Human: https://www.ncbi.nlm.nih.gov/gene/2539

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