You are examining a 6-month-old infant who is experiencing feeding difficulty and generalized hypotonia of the limbs. Additional symptoms reported to you by the infant's parents are strange eye movements tending to cause the eyeballs to rotate up that occur several times a day. Laboratory results indicate significant aminoaciduria and aminoacidemia. Which of the following enzymes is most likely defective in the infant?

Question

Quizplus · Accepted Answer

In the peroxisomes of mammalian tissues, especially liver, there exists a minor enzymatic pathway for the removal of amino groups from amino acids. l-amino acid oxidase is FMN-linked and has broad specificity for the l-amino acids. A number of substances, including oxygen, can act as electron acceptors from the flavoproteins. If oxygen is the acceptor the product is hydrogen peroxide, which is then rapidly degraded by the catalases found in liver and other tissues. Missing or defective l-amino acid oxidase is commonly associated with oculogyric crisis (OGC; spasmodic movements of the eyeballs that lasts several minute to hours) and causes generalized hyperaminoacidemia and hyperaminoaciduria, generally leading to neurotoxicity and early death.

You Are Examining a 6-Month-Old Infant Who Is Experiencing Feeding