I don’t believe that a cat marks with urine. I think it comes from a gland, and they squirt it on whatever. It is difficult to wash off, but can be. It is sprayed on windows, walls, cars, trees, flowers, and even the sidewalk.
There are several bacterial/enzyme products sold today that will consume the smelly organic part of pet and people urine. Anti-Icky-Poo (sic) is one which I have used with great success. As long as some moisture is present, the bacteria multiply and follow the source of odor, consuming it as they go, then they die. The bacteria used does not infect pets or persons.