You are correct, animal-derived enzymes are generally active in a much narrower pH range, so they will only work in the environment with that pH. Additionally, they can become denatured and not work at all if they are in an environment which varies too much from that pH. Microbial and plant-derived enzymes tend to work under a wider range of conditions. This is why they are usually the preferred choice for digestive supplements. Especially when a supplement includes a range of enzymes, they can be active throughout the pH changes of the digestive tract. The stomach has a very low pH, but the pH in the small intestine is much higher. Many animal-derived enzymes may be active in one or the other, but will not work in both (and may get denatured in the acidity of the stomach, therefore never even being active in the small intestine).
