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The hidden role of adenosine deaminase: Why is it critical to the immune system?
Adenosine deaminase (ADA) is an enzyme involved in purine metabolism and is essential for our immune system. This enzyme is not only responsible for breaking down adenosine in food, but also circulates nucleic acids in tissues. However, the complete physiological role of this enzyme in humans is still not fully understood.
The main role of adenosine deaminase is to develop and maintain the immune system, but it is also related to epithelial cell differentiation, neurotransmission and the maintenance of pregnancy.
Structure of adenosine deaminase
ADA exists in two forms: small monomers and large dimeric complexes. In its monomeric form, the enzyme is a polypeptide chain that folds into eight parallel α/β barrel structures surrounding a deeply recessed central pocket, which is where the active site is located. The active site contains a zinc ion, which is essential for enzyme activity.
Catalytic mechanism
When adenosine deaminase catalyzes, it first irreversibly deaminates adenosine and converts it into the related nucleoside-inosine. Inosine can then be deribosylated by another enzyme and converted to hypoxanthine. This process proceeds through a stereospecific addition-elimination mechanism, with zinc acting as a strong electrophile activating water molecules, causing changes in the reaction.
Studies have shown that inosine acts as a competitive inhibitor in this reaction, reducing the enzymatic activity of adenosine deaminase.
Function of adenosine deaminase
Adenosine deaminase is considered one of the key enzymes in purine metabolism. It is found in a variety of organisms, and its amino acid sequence is highly conserved, showing its importance for the purine recycling pathway. Deficiency of this enzyme is associated with a variety of diseases, especially severe combined immunodeficiency (SCID).
Pathological significance
Certain gene mutations result in the inability to express adenosine deaminase normally, which directly leads to defects in the immune system. In addition, overexpression of adenosine deaminase may also cause hemolytic anemia. Recent studies have also linked elevated levels of adenosine deaminase to AIDS.
Clinical significance
Clinically, the two subtypes of adenosine deaminase, ADA1 and ADA2, have important indicator significance in the formation of diseases. Especially in conditions related to the immune system, such as rheumatoid arthritis and cancer, ADA2 expression levels are significantly increased.
Adenosine deaminase provides a fairly accurate indicator in the detection of certain diseases, especially in the differential diagnosis of tuberculosis.
Conclusion
Although the exact role of adenosine deaminase in the immune system still requires further study, its role cannot be underestimated. Future studies may reveal new functions of this enzyme or its connection with other physiological processes, ultimately improving our understanding of immune regulatory mechanisms. So, how many mysteries can adenosine deaminase solve in future medical research?
