Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
Parents bring in their 2-week-old child fearful that he has ingested a poison. They had delayed disposing one of the child™s diapers, and noted a black discoloration where the urine had collected. Later, they realized that all of the child™s diapers would turn black if stored as waste for a day or so. Knowing that phenol groups can complex to form colors, which amino acid pathways are implicated in this phenomenon?
Options:
1. The phenylalanine, tyrosine, and homogentisate pathway
2. The histidine pathway
3. The leucine, isoleucine, and valine pathway
4. The methionine and homocystine pathway
5. The arginine and citrulline pathway (urea cycle)
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
The Correct Answer is: The phenylalanine, tyrosine, and homogentisate pathway
Explanation:
Lack of the enzyme homogentisate oxidase causes the accumulation of homogentisic acid, a metabolite in the pathway of degradation of phenylalanine and tyrosine. Homogentisate, like tyrosine, contains a phenol group. It is excreted in the urine, where it oxidizes and is polymerized to a dark substance upon standing. Under normal conditions, phenylalanine is degraded to tyrosine, which is broken down through a series of steps to fumarate and acetoacetate. The dark pigment melanin is another end product of this pathway. Deficiency of homogentisate oxidase is called alkaptonuria (black urine), a mild disease discovered by Sir Archibald Garrod, the pioneer of biochemical genetics. Garrod™s geneticist colleague, William Bateson, recognized that alkaptonuria, like nearly all enzyme deficiencies, exhibits autosomal recessive inheritance.
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
Dear Kola
Your answer is correct but there is a mistake.
melanin is not end product of this pathway. No doubt tyrosine is converted into pathway but that is a different one from this degradation pathway.
