The OE ( output enable) is active high CMOS high input impedance pin for most of the TXS and TXB devices.
The OE is referenced to Vcca supply w.r.t the voltage levels. i.e The Vih and Vil is ~0.7*Vcca and 0.35*Vcca.
The OE is over voltage tolerant and hence can be connected to Vccb supply, which in most cases, usually higher than Vcca. Care must be taken to ensure that the OE pin's logic levels are maintained as noted to ensure proper operation.