Update: 1/11/11, 6:15 p.m., Another Indian legal news publication, Legally India, reported Tuesday that several more firms were involved in the transaction. According to that report, Linklaters and Bangalore boutique Lexygen advised a consortium of bidders–led by the Carlyle Group–which lost out on Patni in the end. Also, JSA partner Somasekhar Sundaresan was joined by Day Pitney in representing the company’s chairman, while Wadia Ghandy & Co. advised Patni’s board of directors.

Private equity firm General Atlantic, which sold its 17.4 percent stake in Patni, was represented by S&R Associates and Paul, Weiss, Rifkind, Wharton & Garrison, the article said.

Subsidiaries of California-based technology outsourcing company iGATE Corporation have agreed to acquire a majority stake in Mumbai-based IT services company Patni Computer Systems Ltd.

The deal, announced Monday, is valued at $1.22 billion and is expected to close in the first half of 2011. The offer from iGate, which reported revenues of $252 million in the fiscal year ending September 30, relies on funds advised by U.S. private equity firm Apax Partners. (Note: Apax is the parent company of ALM Media, which owns and operates The Am Law Daily.)

iGATE will pay roughly $920 million to the founding family of Patni, as well as private equity firm General Atlantic, for a 63 percent stake in the Mumbai company. Then, the company will make an open offer of more than $300 million to pick up an additional stake of 21 percent.

Once completed, the combination of two major technology and business outsourcing companies will number nearly 25,000 total employees worldwide. According to Bloomberg data, the acquisition is the largest ever of an Indian technology company.

Kirkland & Ellis New York-based corporate partner Srinivas Kaushik advised iGATE on the purchase, and corporate partners Frederick Tanne and Susan Zachman advised Apax Partners. Kirkland corporate partners Jay Ptashek, Neel Sachdev, Joshua Korff, and Michael Kim served as debt financing counsel for iGATE. Haigreve Khaitan of Khaitan & Co. served as local Indian counsel for iGATE, according to Kirkland spokesperson Kate Slaasted.

Indian firm AZB & Partners advised Patni and its founding family, according to a report in Indian legal news publication Bar & Bench. According to that report, AZB’s team was led by partner Essaji Vahanvati; and Patni’s chairman and CEO, Narendra Patni and Jeya Kumar, respectively, were represented by J. Sagar & Associates securities and private equity partner Somasekhar Sundaresan.