Phosphorene is a two-dimensional material that has many advantageous electronic, electrochemical, and optical properties. However, phosphorene possesses a relatively poor stability in ambient atmosphere. This disadvantage limits its application in several systems and particularly in electrochemical biosensors. Here we evaluate phosphorene as an electrochemical biosensing platform in two different mediator-based oxidoreductase enzymatic systems (glucose oxidase (GOx) and peroxidase from horseradish (HRP)), in which their detection is based on the reduction or oxidation of a mediator. In both cases, the used mediator is the same, ferrocene methanol (FcMeOH). Enhanced electrochemical activity is observed only in the reductive system (HRP-based biosensor) when compared to the oxidative counterpart (GOx-based biosensor). This phenomenon is attributed to the fact that in a reductive environment the phosphorene structure remains intact, while in an oxidative potential, the phosphorene is readily oxidized. In this way, the electroactivity of phosphorene as a sensing platform is strongly dependent on the type of mediator-based enzymatic system. These findings of binary nature of phosphorene are of high importance for construction of phosphorene-sensing platforms and in the development of enzyme logic systems.