Copper

• Copper – cofactor for enzymes (lysyl oxidase), electron transport proteins (cytochrome c oxidase) and antioxidant molecules (superoxide dismutase).
• Primarily absorbed through the small intestine and stomach (upper small intestine in the dog).
• Enterocyte regulation of absorption – metallothionein and a copper transport protein – ATPase7A.
• Metallothionein is a low molecular wt cytoplasmic protein, in all tissues; expression in response to heavy metals, various hormones and stress. metallothionein in cytoplasm of enterocytes leads to absorption of copper.
• ATPase7A – transmembrane copper transporter in a number of cell types.
• Defective in people with Menke’s disease – the animal model is the mottled mouse – results in faulty transport of copper out of the cell –leads to copper accumulation in enterocytes. Liver and brain that have little of the transporter experience copper deficiency.
• Chronic diet excess of copper leads to accumulation in the liver .
• Serum copper – in 2 pools
  • Exchangeable pool – loosely bound to carrier molecules; 80% of it bound to transcuperin, the rest bound to albumin.
  • Other pool – tightly bound to carrier molecules.