In 2002 a paper by Vickers et al reported that Fluoride and Chloride, but not Bromide enhanced the activity of the ACE2 enzyme, a Zinc metalloprotease.
Hydrolysis of Biological Peptides by Human Angiotensin-converting Enzyme-related Carboxypeptidase
https://www.jbc.org/content/277/17/14838.full.html
What mechanism is behind this observation? Does Fluoride bind to the Zinc atom of the enzyme, or perhaps help to remove a proton from a water molecule bound to Zinc via formation of HF?
Would Chloride have a similar effect? Why does Bromide not behave in the same way?