Answer :
Final Answer:
Darkening of urine upon air exposure is due to an enzyme deficiency called "alkaptonuria," causing homogentisic acid accumulation. This rare disorder affects tyrosine breakdown and aids in diagnosis.
Explanation:
Alkaptonuria is a rare inherited metabolic disorder caused by the deficiency of the enzyme homogentisate 1,2-dioxygenase. This enzyme is crucial in the breakdown of an amino acid called tyrosine. In individuals with alkaptonuria, the absence of this enzyme leads to the accumulation of a compound called homogentisic acid in the body.
Homogentisic acid is normally processed and excreted in the urine. However, due to the enzyme deficiency, it is not properly metabolized and can darken upon exposure to air. When urine containing excess homogentisic acid is exposed to oxygen in the air, a chemical reaction occurs, causing the urine to turn dark upon standing. This darkening effect is often described as "ochronosis" and is particularly noticeable when the urine is left standing for some time.
The darkening of urine is not harmful in itself but is a characteristic sign of alkaptonuria. People with alkaptonuria may also experience other symptoms, including joint and connective tissue problems, due to the deposition of homogentisic acid in these tissues.
In conclusion, the enzyme deficiency known as alkaptonuria leads to the darkening of urine when exposed to air due to the accumulation of homogentisic acid, a byproduct of incomplete tyrosine metabolism. This condition is rare but distinctive, and its diagnosis is often made through clinical observation and specialized testing.
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