any hydrolase enzyme, as pepsin or trypsin, that acts as a catalyst in chemical reactions in which a protein is broken down by hydrolysis
Origin:
prote(in) + (diast)ase
See protease in American Heritage Dictionary 4
noun
Any of various enzymes, including the endopeptidases and exopeptidases, that catalyze the hydrolytic breakdown of proteins into peptides or amino acids.