A 29-year-old man is being examined by his physician to determine the cause of his progressing tremors. His physician notes that the man has a diminished capacity to move his facial muscles and that the tremors in his arms are indicative of choreoathetosis. Serum analysis shows significantly elevated AST and ALT. Ophthalmic examination indicates that the patient has Keyser-Fleischer rings in his corneas suggesting he is suffering from Wilson disease. The lack of which of the following processes would most likely be found in this patient?

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The patient is likely suffering from Wilson disease, which is characterized by a deficiency in the incorporation of copper into ceruloplasmin, leading to copper accumulation in tissues. Wilson disease is the result of defects in the P-type ATPase protein that is primarily responsible for copper homeostasis within the liver. This protein is encoded by the ATPase, Cu2+-transporting, β-polypeptide (ATP7B) gene. ATP7B facilitates the transfer of copper to the major plasma copper transport protein, ceruloplasmin. In the liver, copper is stored intracellularly bound to the protein metallothionein. Any copper in excess of the binding capacity of metallothionein is excreted into the biliary canaliculi through the transport action of ATP7B. The majority of patients with Wilson disease present with hepatic or neuropsychiatric symptoms. The most significant sign in the diagnosis of Wilson disease results from the deposition of copper in Descemet's membrane of the cornea. These golden-brown deposits can be seen with a slitlamp and are Kayser-Fleischer rings.

A 29-Year-Old Man Is Being Examined by His Physician to Determine