(Reuters) -U.S. mortgage data vendor Black Knight will sell its Optimal Blue business for $700 million, shedding a second unit to soothe regulatory concerns over its proposed buyout by NYSE-owner Intercontinental Exchange.

Canadian business software firm Constellation Software will buy the unit, provided ICE closes its takeover, the companies said on Monday, sending shares of Black Knight to a one-year high of $69.31.

Optimal Blue provides data and technology to price and trade mortgages.

Constellation had also agreed to buy Black Knight's Empower loan origination system business in March, a deal that analysts said may not be enough to quell concerns over ICE's $11.7 billion proposal.

The Federal Trade Commission (FTC) in March vowed to take action against the deal after some U.S. lawmakers warned that the pricing power ICE would gain in the mortgage data market could lead to higher costs for consumers.

ICE and Black Knight have said they are willing to go to court to save their deal, if necessary.

FTC Chair Lina Khan's tough stance on corporate consolidation has made it more difficult for companies to clinch mergers without significant concessions, but the agency has lost some high-profile court battles of late - including one over Microsoft's $69 billion bid for Activision Blizzard.

The losses have emboldened Khan's critics, who have attacked the FTC for being too aggressive and "killing deals in the boardroom."

(Reporting by Niket Nishant in Bengaluru; Editing by Anil D'Silva and Devika Syamnath)