YES. it is designed to provide support the tank and prevent it from bowing and potentially shattering the tank.
I will say that I have a 55 gallon that the brace broke last spring and yes there is a slight bow but it does not seem to effect the tank. However you tank is twice the size so there is more stress on the glass.
I have looked and have not found a replacement piece. You may be able to contact the manufacturer of the tank and order one directly from them.