Real estate mogul Rob Maguire, founder of Maguire Properties Inc., has bought out Equity Office Properties Trust’s 87.5 percent interest in the Water’s Edge office park in Playa Vista for $85.5 million.

EOP disclosed in a release announcing its fourth quarter earnings that Maguire closed on the purchase of its interest in the prime Westside office park last month. Maguire, who developed the property and handled the leasing, bought the campus with EOP’s backing from Playa Capital in a deal announced in December 2000.

The acquisition was made by Maguire, who took out a personal loan to fund the transaction, according to Maguire Properties spokeswoman Peggy Moretti. She said the real estate investment trust, which went public last year, provided no money for the deal and had no equity stake in the property. Maguire couldn’t be reached for comment.

Water’s Edge is a 6.5-acre office park at 5510 Lincoln Blvd. that has two buildings totaling 240,000 square feet. The campus has rights for a 192,000-square-foot expansion. Electronic Arts Inc. leases about 85 percent of the complex.

Moretti said Maguire Properties has an option to buy the Water’s Edge complex from its chairman and co-chief executive if it deems the acquisition “appropriate” in rights predating the public offering. “There is a formula for which the company can buy it,” Moretti said. “And that would be discussed at a potentially future date.”

She said the company, in the midst of finalizing a deal to buy the 10-building portfolio of CommonWealth Properties LLC, isn’t considering buying the property.

“Our immediate focus is to execute the CommonWealth properties portfolio acquisition,” she said. “The company is not contemplating buying Water’s Edge at this time.”