Maguire Properties Inc. announced Wednesday it’s forming a $1.2 billion joint venture with Macquarie Office Trust, a large Australian real estate owner.

The new entity, Maguire Macquarie Office, will own six buildings, mostly in Southern California, that comprise 4 million square feet and have a combined asset value of $1.2 billion.

The transaction, expected to be complete by year’s end, will generate net proceeds to Maguire of $350 million, according to a company statement.

Since early this year, Maguire has been seeking an Australian joint venture to ease its debt-to-earnings ratio, which ranks the company as one of the highest leveraged real estate firms traded on Wall Street.

Robert F. Maguire III, chairman and chief executive of Maguire Properties, said in the company’s statement that the new venture also will seek new acquisitions.

Five of the buildings in the portfolio belonged to Maguire, which will retain a 20 percent stake in the new venture and will manage the properties.

Maguire’s buildings in the joint venture are: One California Plaza in downtown L.A., Cerritos Corporate Center in Cerritos, Washington Mutual Campus in Irvine, the San Diego Tech Center in San Diego and the Wells Fargo Center in Denver, Colo.

Macquarie is contributing its Stadium Gateway building in Anaheim. Maguire, the largest owner of office buildings in downtown’s Bunker Hill, was advised by Deutsche Bank in the transaction.