Ram usage and mysql processes

RT 3.4.2 On Fedora Core 3

Recently I have noticed that there are about 12 to 15 mysql processes
running on my RT server. Is there a way to limit these processes? I have
limited my httpd to 4 processes but I do not know how to limit the mysqld
processes? All of the mysqld process are using 4.5% of the RAM so needless
to say it is eating up alot of my ram…

Any help would be great…