The acquisition values venture capital-backed Fixnetix at about £100 million, possibly including debt and potential price adjustments, according to a source with knowledge of the deal. The agreement includes an option for NYSE to buy the remaining 75% stake by the end of 2015.

The move for Fixnetix is the first expression of a post-Deutsche Börse strategy from NYSE chief executive Duncan Niederauer, who said last week that technology services were at the heart of his growth strategy. Revenue at the group's NYSE Technologies unit should increase by more than 10% this year, from $490 million in 2011, making it the company's fastest-growing operation by that measure.

NYSE Technologies and its counterparts at other stock market operators have prospered as clients such as hedge funds, brokers and fund managers increasingly outsource the management and provision of their trading networks.

Fixnetix provides outsourced services for ultra-fast trading, as well as market data, hosting and infrastructure for client networks. Revenue at the group was about £25 million in 2011, up from about £1 million in 2008. "This strategic shareholder interest in Fixnetix aligns with our mission to build a global capital markets community supported by world-class technology, broad connectivity and diverse customer participation that yields greater liquidity and market innovation," NYSE Technologies chief executive Stanley Young said in a statement.

Niederauer said last week that he had been working on alternative deals in the event that Deutsche Börse was unable to conclude its acquisition. The European Commission, Europe's antitrust regulator, killed that transaction on Feb. 1.

London-based Fixnetix was founded in 2006 by three partners: CEO Hugh Hughes, a former chief executive of SG Securities, a unit of French bank Société Générale SA; chief operating officer Paul Ellis, formerly of ABN Amro; and Alasdair Moore. The company has been in talks with NYSE since November after its owners signaled that they would consider a partial or full sale.

Fixnetix VC backers, including Thematic Capital Partners LLP and Delta Partners, will reduce their holdings in the deal with NYSE.