  We propose an interband tunneling picture to explain and predict the
interlayer twist angle dependence of the induced spin-orbit coupling in
heterostructures of graphene and monolayer transition metal dichalcogenides
(TMDCs). We obtain a compact analytic formula for the induced valley Zeeman and
Rashba spin-orbit coupling in terms of the TMDC band structure parameters and
interlayer tunneling matrix elements. We parametrize the tunneling matrix
elements with few parameters, which in our formalism are independent of the
twist angle between the layers. We estimate the value of the tunneling
parameters from existing DFT calculations at zero twist angle and we use them
to predict the induced spin-orbit coupling at non-zero angles. Provided that
the energy of the Dirac point of graphene is close to the TMDC conduction band,
we expect a sharp increase of the induced spin-orbit coupling around a twist
angle of 18 degrees.
