Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation?

• A. Succinylcholine must be an allosteric regulator for this enzyme.
• B. The active site must have the wrong configuration to permit succinylcholine binding.
• C. Succinylcholine must be a noncompetitive inhibitor.
• D. The presence of succinylcholine changes the conditions in the solution, resulting in a denaturation of the enzyme.
• E. Succinylcholine must be a competitive inhibitor with acetylcholine.