If you own a pedigreed cat and want to breed your cat, obviously you will not have him or her neutered. But if you have no intention of breeding—ever—you should have your cat neutered, for reasons discussed elsewhere in this blog.
The usual rule is to have the cat neutered before the cat reaches sexual maturity, but owners of pedigreed cats sometimes wait until after that time. The assumption is that the animal will not develop all the attractive traits of the breed if neutered before puberty.