In addition to chloride, which anion serves as an enzyme activator?

• A. Bromide
• B. Fluoride
• C. Nitrate
• D. Iodide

Answer: (A)

Some enzymes need a halide ion to reach full activity. Chloride is the classic activator for several enzymes, helping the catalytic site function properly. Bromide is the closest analogue to chloride, and because of its similar size and charge, it can bind in the same way and support catalysis. That’s why bromide can act as an enzyme activator in addition to chloride.

Fluoride often inhibits enzymes or alters activity rather than acting as an activator. Nitrate doesn’t typically fit the enzyme’s activating binding site, and iodide’s larger size can disrupt the precise interactions needed for activation. So bromide is the best fit as the other activating anion.