Commutative subalgebras of $U(\mathfrak q)$ of maximal transcendence degree

We prove that the enveloping algebra $U(\mathfrak q)$ of a finite-dimensional Lie algebra $\mathfrak q$ contains a commutative subalgebra of the maximal possible transcendence degree $(\dim\mathfrak q+ \mathrm{ind}\,\mathfrak q)/2$.