An enzyme catalyzes the reaction X → Y + Z. In a series of experiments, it was found that substance A inhibits the enzyme.
When the concentration of X is high and A is low, the reaction proceeds rapidly and Y and Z are formed.
As the concentration of A increases, the reaction slows regardless of whether X is present in high or low concentrations.
If the concentration of A is high (relative to X), the reaction stops.
If the concentration of A decreases again, the reaction will ultimately resume.

What type of enzyme regulation is described here? Explain your answer.