I think that this is interesting.

It has been known for some time that α-synuclein can bind a range of metal ions. It has been argued that this may lead to production of Reactive Oxygen Species (ROS) which may lead to neuronal damage in people with PD; this is a recent, somewhat technical, paper about this Alpha-Synuclein Oligomers Interact with Metal Ions to Induce Oxidative Stress and Neuronal Death in Parkinson's Disease.

It is possible (though speculative) that the low levels of Zn2+ in people with PD may allow α-synuclein to preferentially interact with redox-active metal ions like Fe3+ and Cu2+, leading to generation of ROS.