I hunt in Minnesota, where it is illegal to use the .45 ACP for deer.
Much like the .223 for deer hunting debate, the .45 auto is capable of killing a deer, but it must be a PERFECT shot to do so. The .45 ACP, even loaded pretty warm, still does not pack the whallop you really need for a humane kill.
The absolute minimum I would even consider for deer hunting is a .357 Mag with some really hot 180 grain loads. A .41 mag or .44 mag would be the preferred caliber.