Yes, PEPTIDASE is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, P 3, T 1, I 1, D 2, A 1, S 1, E 1.

Is it a valid word?

PEPTIDASE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any enzyme that catalyzes the splitting of proteins into smaller peptide fractions and amino acids by a process known as proteolysis

Also: proteolytic enzyme.