The word "synaptase" is spelled with a "y" and "t" rather than an "i" and "s" because it is derived from the word "synapse." The "y" represents the sound /aɪ/ and the "t" represents the sound /t/. The ending "-ase" indicates that it is an enzyme, which is a type of protein that speeds up chemical reactions. Synaptase is an important enzyme found in the synapses of neurons, where it helps to break down neurotransmitters.
Emulsin.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.