I'm trying to run the gem command with sudo, why doesn't it work?

levander@bread:~ $ sudo echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11:/usr/games:/opt/rubygems/bin
levander@bread:~ $ sudo gem
sudo: gem: command not found
levander@bread:~ $ ls -l /opt/rubygems/bin/gem
-rwxr-xr-x 1 root root 701 2006-09-07 22:00 /opt/rubygems/bin/gem