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Old 08-25-2011
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Default enzyme defct

A child with white hair, very pale skin, and blue eyes undergoes an ophthalmologic evaluation and is diagnosed with strabismus and 20/400 vision. The patient is otherwise healthy and demonstrates no evidence of neurologic defects. To account for these findings, which enzyme could be defective?
A. Cystathionine synthetase
B. Tyrosine hydroxylase
C. Homogentisic acid dioxygenase
D. Tyrosinase
E. Phenylalanine hydroxylase
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Old 08-25-2011
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Default tyrosinase?

albinism = lack of tyrosinase?

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Originally Posted by ricko335 View Post
A child with white hair, very pale skin, and blue eyes undergoes an ophthalmologic evaluation and is diagnosed with strabismus and 20/400 vision. The patient is otherwise healthy and demonstrates no evidence of neurologic defects. To account for these findings, which enzyme could be defective?
A. Cystathionine synthetase
B. Tyrosine hydroxylase
C. Homogentisic acid dioxygenase
D. Tyrosinase
E. Phenylalanine hydroxylase
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Old 08-25-2011
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D) tyrosinase - melanin synthesis.
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Old 08-26-2011
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tyrosinase
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Old 08-26-2011
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Yep, agree with Tyrosinase!
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Old 08-26-2011
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tyrosinase......albinism
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Old 08-28-2011
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The correct answer is D.
This child has oculocutaneous albinism, which is most classically due to tyrosinase deficiency. While both tyrosinase and tyrosine hydroxylase produce L-DOPA, which is a precursor for melanin, it is tyrosinase that moves Tyr into the melanin pathway by further converting L-DOPA to DOPA-oxidase (a second reaction).
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