I read on another site a blog from a long-time cat owner that she had started using (with apparent huge success) rubbing alcohol as a remover for cat urine from upholstery.
She just poured it on the stain, blotted up the excess then left the thing to dry (well ventilated) and as if by magic the smell disappeared.
Apparently rubbing alcohol (isopropyl alcohol) is the main ingredient in many enzymic odour removing fluids.
Any truth in this? With 5 boy cats in the house, pee spray on furniture is a constant problem for me (and my Mother's coming to stay on Friday!)