  Motivated by the recent proposed models of the information engine [D. Mandal
and C. Jarzynski, Proc. Natl. Acad. Sci. 109, 11641 (2012)] and the information
refrigerator [D. Mandal, H. T. Quan, and C. Jarzynski, Phys. Rev. Lett. 111,
030602 (2013)], we propose a minimal model of the information pump and the
information eraser based on enzyme kinetics. This device can either pump
molecules against the chemical potential gradient by consuming the information
encoded in the bit stream or (partially) erase the information encoded in the
bit stream by consuming the Gibbs free energy. The dynamics of this model is
solved exactly, and the "phase diagram" of the operation regimes is determined.
The efficiency and the power of the information machine is analyzed. The
validity of the second law of thermodynamics within our model is clarified. Our
model offers a simple paradigm for the investigating of the thermodynamics of
information processing involving the chemical potential in small systems.
