The effect of metals on the activity of L-phenylalanine hydroxylase

The effects of 12 metals other than iron on the native (iron-containing) L-phenylalanine Hydroxylase from rat liver have been measured. The metals were tested in vivo at 10X and 100X molar excess. The effects generally are moderate deactivation of the enzyme; mercury and copper are particularly deactivating while rubidium is slightly activating. Complete restoration of the activity to the apoenzyme can only be achieved by iron(II). However, partial restoration is achieved by aluminium, thallium and cadmium. While restoration of activity under anaerobic conditions can also be achieved by iron(III), the increase in restoration ability of other transition metals under anaerobic conditions is not great. The restoration ability of rubidium increases, surprisingly, under anaerobic conditions.