"It's a 5-year-old business that they always knew was going to end," Leslie Sloane-Zelnick, a publicist for the actress, said Thursday.
There was no formal announcement but word first circulated about a month ago.
"They still remain good friends," Sloane-Zelnick said. "The timing was due to the fact that they have other projects in their lives right now and they live on separate coasts. And this is what they always planned."
Last September, the two were on hand at New York Fashion Week, presenting only 14 spring looks in a Chelsea gallery, but they didn't show at fashion week last month.
The reason? Closing down Holmes & Yang was "in the works," Sloane-Zelnick said. "They have different lives now."
Holmes was on hand in New York in February to attend Donna Karan's anniversary show.
Holmes and Yang described the fashion mix they offered last fall as "wearable elegance," including a black silk V-neck gown with leather piping and a khaki camp-style shirtdress with a lace-up V at the neck. There was a bralette paired with a tie-front blazer and men's-style trousers.
Nowadays, Yang is busy "styling major people in LA," the publicist said, and Holmes is in a movie about a school teacher, "Miss Meadows," that will premiere next month at the 13th annual Tribeca Film Festival. In addition, the "Dawson's Creek" actress plans a return to TV in a starring role, in an ABC pilot for a drama about a New York City socialite.