ADH requires the presence of a nicotinamide adenine dinucleotide (NAD+) molecule in order to catalyze the oxidation of an alcohol. Because NAD+ is converted to NADH and released, it is a cosubstrate of the reaction, and NADH is a coproduct. Additionally, like many enzymes, ADH requires a metal cation for catalysis, which in this case is zinc (Zn2+). Zn2+ is not altered by ADH, nor is it tightly bound to the enzyme. Which term best describes the role of Zn2+ in the reaction catalyzed by ADH? prosthetic group cofactor cosubstrate coenzyme