ACYLPHOSPHATE FORMATION BY THE MENKES COPPER ATPASE

The Menkes ATPase is the product of the MNK gene, defective in some in herited human disorders of copper metabolism. We here show the formati on of an acylphosphate intermediate by the murine MNK homologue in mem branes from normal and copper resistant Chinese hamster ovary cells. I n the latter, fivefold higher levels of acylphosphate were formed. Cha llenging these cells with copper, which induces relocation of the MNK ATPase from the trans-Golgi network to the plasma membrane, did not in fluence acylphosphate formation. The kinetics of phosphorylation, meta l dependence, and sensitivity to inhibitors were investigated. The res ults show that the MNK ATPase is an active P-type ATPase and provide a direct functional test for this enzyme. (C) 1997 Federation of Europe an Biochemical Societies.