Hi Susanne
No the 4500 does not support full MPLS/VPN. It will support vrf-lite which is a subset of MPLS to an extent.
The only switches that support MPLS are the 3750 Metro and the 6500.
If you go to http://www.cisco.com/go/srnd
and have a look at the "Network Virtualisation--Path Isolation Design Guide" there is a lot more information in here about switch support for MPLS and vrf-lite.
HTH
Jon