Metal Gear Rising is being released on the Mac platform today, and is the first Metal Gear game to be available for Mac. The game was ported to Mac by a company named TransGaming Inc., in partnership with Konami.
TransGaming is a company that specializes in technological services such as source code licensing and support for enablement of PC games and DirectX-based content on Android, iOS and SteamOS platforms. The Mac port of Rising is their first game release.
You can grab Metal Gear Rising for $29.99 off the Mac App Store or on Steam. Until September 30th, the game is being discounted by $5.