  For each positive integer $n$, let $\mathfrak{s}_n=\mathfrak{gl}_n\ltimes
\mathbb{C}^n$. We show that $U(\mathfrak{s}_{n})_{X_{n}}\cong
\mathcal{D}_{n}\otimes U(\mathfrak{s}_{n-1})$ for any $n\in\mathbb{Z}_{\geq
2}$, where $U(\mathfrak{s}_{n})_{X_{n}}$ is the localization of
$U(\mathfrak{s}_{n})$ with respect to the subset $X_n:=\{e_1^{i_1}\cdots
e_{n}^{i_{n}}\mid i_1,\dots,i_{n}\in \mathbb{Z}_+\}$, and $\mathcal{D}_{n}$ is
the Weyl algebra $\mathbb{C}[x_1^{\pm 1}, \cdots, x_{n}^{\pm 1},
\frac{\partial}{\partial x_1},\cdots, \frac{\partial}{\partial x_{n}}]$. As an
application, we give a new proof of the Gelfand-Kirillov conjecture for
$\mathfrak{s}_n$ and $\mathfrak{gl}_n$. Moreover we show that the category of
Harish-Chandra $U(\mathfrak{s}_{n})_{X_n}$-modules with a fixed weight support
is equivalent to the category of finite dimensional
$\mathfrak{s}_{n-1}$-modules whose representation type is wild, for any $n\in
\mathbb{Z}_{\geq 2}$.
