  A novel mechanism of reaction-induced active molecular motion, not involving
any kind of self-propulsion, is proposed and analyzed. Because of the momentum
exchange with the surrounding solvent, conformational transitions in
mechano-chemical enzymes are accompanied by motions of their centers of mass.
As we show, in combination with rotational diffusion, such repeated reciprocal
motions generate an additional random walk - or molecular dancing - and hence
boost translational diffusion of an enzyme. A systematic theory of this
phenomenon is developed, using as an example a simple enzyme model of a rigid
two-state dumbbell. To support the analysis, numerical simulations are
performed. Our conclusion is that the phenomenon of molecular dancing could
underlie the observations of reaction-induced diffusion enhancement in enzymes.
Major experimental findings, such as the occurrence of leaps, the
anti-chemotaxis, the linear dependence on the reaction turnover rate and on the
rate of energy supply, become thus explained. Moreover, the dancing behavior is
possible in other systems, natural and synthetic, too. In the future,
interesting biotechnology applications may be developed using such effects.
