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Biochemistry

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Phenylketonuria (PKU) and Aspartame

BIOCHM-TWJ8HJ

Phenylketonuria or PKU is an autosomal recessive condition resulting from one of a number of mutations in the gene encoding the amino acid converting enzyme phenylalanine hydroxylase (PheOH). PheOH requires the cofactor tetrahydrobiopterin (BH4). All newborns are tested for PKU at birth. Untreated PKU will lead to permanent neurological damage.

Consider the likely biochemical reaction catalyzed by PheOH and then identify ALL of the following statements which are NOT true concerning untreated individuals testing positive for PKU.

Select ALL that apply.

A

Individuals testing positive for PKU likely have a high ratio of Phe/Tyr in their blood.

B

Individuals testing positive for PKU would benefit from a high protein diet.

C

Individuals testing positive for PKU would be harmed by consuming diet food or drink containing the digestable artificial sweetener aspartame (see structure below).

Cacycle. Chemical Structure of Aspartame. Wikimedia Commons, 13 June 2007. Web. 22 Aug. 2016.

D

Individuals testing positive for PKU would benefit from a low carbohydrate diet.

E

Protein synthesis in individuals testing positive for PKU would likely be impacted due to limiting amounts of the amino acid threonine.

F

Individuals testing positive for PKU would be harmed by consuming diet food or drink containing the undigestable artificial sweetener sucralose (see structure below).

Harbin. "File:Sucralose2.svg." Wikimedia Commons. 2D Structure of Artificial Sweetener Sucralose., 19 Jan. 2009. Web. 22 Aug. 2016. https://commons.wikimedia.org/wiki/File:Sucralose2.svg.

G

PKU individuals with a defective (low-functioning) phenylalanine hydroxylase (PheOH) enzyme would likely benefit from taking Kuvan, a synthetic version of the cofactor BH4.