Why is chloride ion classed as a cofactor for amylase rather than as a coenzyme?
On the wikipedia page (en.wikipedia.org/wiki/Cofactor_(biochemistry)) a coenzyme is defined as a complex organic cofactor, so Cl⁻ doesn't count. Another thing that disqualifies it as a coenzyme is that the ion is not directly involved in the catalyzed reaction. This amylase contains both a calcium ion, involved in catalysis. The chloride is speculated only to be involved in differentiation between substrates, and is absent in other structures.