OPA991: What to do with SHDN Pin?

I am hoping to transition from an opa171 soic-8 opamp into an OPA991 SOT-23-6 package.

I am very puzzled with one of the pins though which only exists on the 6 pin version. Pin 5, labelled SHDN (Pin 5). What to do I do to that pin? 

The circuit is to be run off of a single supply batterie and is wired as an inverting summing amplifier.

Do I need to load aschematic? It's literallya specific parts function that I do not know what to do with it.

Thank you guys, hopefully someone can shine some light on this.