Final answer:
The missing catalytic activity in the inactive enzyme that is similar to a protease is a hydrolase.
Step-by-step explanation:
The enzyme that is similar to a protease but inactive is missing the catalytic activity of a hydrolase. Hydrolases are enzymes that catalyze the breakage of bonds with the addition of water. Since a protease is an enzyme that breaks down proteins, it falls under the category of hydrolases. Therefore, if an enzyme is similar to a protease but inactive, it is most likely missing the hydrolase activity.