I am fairly small and I am in animal cells. I help the animal cells break down molecules by emptying out my enzymes to speed up reactions. I am very helpful. What am I?

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.