Yes, SUBMITTERS is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, B 3, M 3, I 1, T 1, T 1, E 1, R 1, S 1.

Is it a valid word?

SUBMITTERS is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

someone who yields to the will of another person or force
someone who submits something (as an application for a job or a manuscript for publication etc.) for the judgment of others