U.S. private equity firm Blackstone Group LP will buy commercial real estate manager Gramercy Property Trust in a $7.6 billion all-cash deal, the companies said on Monday.

Blackstone's $27.50-per-share offer represents a premium of 15.4 percent to Gramercy's close on Friday at $23.82.

The deal will add to Blackstone's real estate business, which has emerged as a bigger contributor to earnings in recent years than its private equity division.

Blackstone earlier this year elevated Jonathan Gray, who turned the buyout firm into the world's biggest real estate investor, to president and chief operating officer, setting him up as successor to CEO Stephen Schwarzman.

The acquisition has an equity value of $4.42 billion, according to Reuters' calculations. Gramercy's total liabilities, as of March 31, were $3.14 billion.

Gramercy's shareholders will receive a second-quarter dividend of 37.5 cents per share.

The deal is expected to close in the second half of the year, Gramercy said.

Morgan Stanley was Gramercy's financial adviser, while Citigroup and BofA Merrill Lynch advised Blackstone.