Canada's national pension plan is part of a group buying U.S. pet store chain Petco for almost $5 billion US.

The Canada Pension Plan and Investment Board and private equity firm CVC Capital Partners Ltd. announced a deal to buy the chain, which is valued at $4.6 billion US.

Currently, Petco is owned by private equity firms TPG Inc. and Leonard Green & Partners LP, who took the chain private in 2006 in a deal that valued the company at $1.7 billion then.

Earlier this year, Petco announced it had hired advisers to look into strategic options for the company, which included either a sale to an outside buyer or a return to public markets in an IPO.

With 1,400 stores, Petco is the second-largest chain of pet stores in America after PetSmart, which was itself taken private last year in a deal that valued the company at $8.2 billion.

Quebec's pension plan Caisse was one of the parties that took a stake in PetSmart at the time.

The two pet store chains had reportedly considered a merger before that possibility was squashed due to regulatory concerns about a lack of competition in the pet industry, which is estimated to be worth as much as $75 billion in the U.S.

"As the North American pet industry continues to grow, Petco is well positioned with a strong brand, differentiated engagement model, and omnichannel strategy," Petco CEO James Myers said in a release.