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Biochemistry

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Phenylketonuria (PKU) and Toxin Resistance

BIOCHM-1QWPQH

Ochratoxin A (OTA) is a mycotoxin or mold produced by a variety of fungi. When inhaled or consumed in tainted food, it can lead to severe kidney and liver damage. It is of particular concern in regions where persistent rainfall and moist conditions are routinely encountered.

Ochratoxin (OTA) is a competitive inhibitor of the protein synthesis reaction catalyzed by phenylalanyl-tRNA synthetase. Interestingly, people with the autosomal recessive inherited condition PKU (phenylketonuria) and some carriers of PKU exhibit resistance to the damaging effects caused by OTA. It is believed that this has led to the evolutionary conservation of the PKU mutation in the population, especially in Ireland and Scotland, where wet conditions prevail for long periods of time.

Which of the following is the MOST likely explanation for this observed resistance to OTA by people with or carriers of a PKU mutation?

A

The relatively higher levels of Phe produced by people with (or carriers of) the PKU mutation leads to Phe outcompeting OTA for binding to the enzyme.

B

The relatively higher levels of Tyr produced by people with (or carriers of) the PKU mutation leads to Tyr outcompeting OTA for binding to the enzyme.

C

The relatively higher levels of Phe incorporated into proteins of people with (or carriers of) the PKU mutation provides a natural protection against the inhibitory effects of OTA on protein synthesis.

D

The relatively lower levels of Tyr produced by people with (or carriers of) the PKU mutation leads to a lower level of protein synthesis rendering the inhibitory effects of OTA on protein synthesis as inconsequential.

E

The relatively lower levels of Phe produced by people with (or carriers of) the PKU mutation leads to a lower level of protein synthesis rendering the inhibitory effects of OTA on protein synthesis as inconsequential.