Final answer:
Autosomal deficiency of adenosine deaminase is the 2nd most common cause of severe combined immunodeficiency disease (SCID). It leads to an accumulation of a toxin that destroys immune cells. Gene therapy has been used to treat this genetic disorder.
Step-by-step explanation:
The autosomal deficiency of the enzyme adenosine deaminase is the 2nd most common cause of severe combined immunodeficiency disease (SCID), after X-linked defective IL-2R gamma chain. Adenosine deaminase deficiency leads to an accumulation of the toxin deoxyadenosine, which can destroy immune cells, essentially crippling the immune system's ability to fight off infections. One of the pioneering treatments for ADA deficiency involves gene therapy to restore immune function.
The enzyme glucose-6-phosphate dehydrogenase (G6PD) plays a crucial role in the pentose phosphate pathway. It is required for maintaining NADPH and, subsequently, glutathione levels, which protect red blood cells against oxidative damage. A deficiency in G6PD is the most common enzyme-deficiency disorder and can lead to premature destruction of red blood cells, resulting in anemia.
Primary immunodeficiencies, such as ADA and G6PD deficiencies, are genetically inherited, while secondary immunodeficiencies can be acquired from various environmental factors. Disorders such as ADA deficiency highlight the importance of enzymes in cellular metabolism and the severe impact that their deficiencies can have on human health.