Yes, HEMOLYSIN is a Scrabble word!

Letter values in Scrabble US: H 4, E 1, M 3, O 1, L 1, Y 4, S 1, I 1, N 1.

Is it a valid word?

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

any substance that can cause lysis (destruction) of erythrocytes (red blood cells) and the release of their hemoglobin

Also: erythrocytolysin.

Not playable in Scrabble US: HAEMOLYSIN, ERYTHROLYSIN.