• Kim Lubel, CEO of CST Brands Inc., will leave the company now that it has completed its $4.4 billion merger with Alimentation Couche-Tard Inc., the Canadian parent company of Circle K. Photo: San Antonio Express-News File Photo / ©2013 San Antonio Express-News

The Canadian parent company of Circle K convenience stores finalized its $4.4 billion merger with CST Brands Inc. as CEO Kim Lubel announced she is leaving the San Antonio-based convenience store operator.

The CST acquisition is a big get for Quebec-based Alimentation Couche-Tard’s fleet of Circle K convenience stores. After selling off 229 stores to satisfy antitrust regulators in the U.S. and Canada, Couche-Tard will have gained more than 1,300 stores in both countries via the sale, expanding its footprint to almost 9,500 locations including 666 in Texas.

Couche-Tard is in a “race to the top” against 7-Eleven Inc. for consolidating the convenience store market, said Jeff Lenard, a spokesman for the National Association of Convenience Stores. The Irving-based convenience store chain reached 9,815 stores in the U.S. and Canada after agreeing to purchase 1,108 stores from Sunoco for $3.3 billion in April.

“They have both been very aggressive on acquisitions,” Lenard said. “They are almost neck-and-neck now where one transaction may push Couche-Tard past 7-Eleven.”

Couche-Tard Inc. agreed to purchase CST Brands, which operates the Corner Store chain of convenience stores, in an all-cash transaction in August. Couche-Tard won merger approvals from regulators in the U.S. and Canada earlier this week and completed the merger Wednesday. As part of…