Mayer Brown's merger with leading Hong Kong firm Johnson Stokes & Master was the largest of three merger deals involving US law firms to be announced over the Christmas break, in the latest moves by America's top practices to expand beyond their domestic heartland.

Mayer Brown unveiled the news shortly after Paul Hastings Janofsky & Walker made its long-awaited German debut after brokering a deal to absorb a respected 27-lawyer Frankfurt boutique, while Kirkpatrick & Lockhart Preston Gates Ellis sealed a domestic merger with Dallas firm Hughes & Luce.

Mayer Brown's deal will dramatically increase the Anglo-US firm's presence in Asia, handing it a seven-office network with more than 260 lawyers and a turnover of $160m (£81m).

Under the terms of the deal, which will complete on 28 January, Mayer Brown will practise as Mayer Brown JSM in Asia. Elaine Lo, chair of Johnson Stokes' partnership board, will head up a new Asia board as well as joining Mayer Brown's management committee, along with senior litigation partner Nick Hunsworth.

Mayer Brown said the merger meant the firm had already over-delivered on its three-year Asia strategy to build up to 100 lawyers, having opened a small office in Hong Kong at the start of the year.

Paul Hastings' agreement with Frankfurt practice Smeets Haas Wolff went live on 3 January. The move marks the end of a long search by Los Angeles-based Paul Hastings to launch in Germany. All five Smeets Haas partners joined Paul Hastings as equity partners. The German outfit focuses on corporate, banking and restructuring work.

Meanwhile, K&L Gates' tie-up with Hughes & Luce went live on 1 January. The deal adds around 150 lawyers along with offices in Fort Worth and Austin to K&L Gates' 1,400-lawyer network.