  Given a Lax system of equations with the spectral parameter on a Riemann
surface we construct a projective unitary representation of the Lie algebra of
Hamiltonian vector fields by Knizhnik-Zamolodchikov operators. This provides a
prequantization of the Lax system. The representation operators of Poisson
commuting Hamiltonians of the Lax system projectively commute. If Hamiltonians
depend only on action variables then the corresponding operators commute.
