Or it could be the other way - our digestive system uses that molecule because it is compatible with our body temperature. If we had a warmer or cooler body temperature, our digestive system might have developed to use another enzyme.

Atlantic cod use a variant, trypsin Y. It has an optimal temperature of 21 C.

https://www.sciencedirect.com/science/article/abs/pii/S0308814608004238

I love how your mind works!