Under terms of the deal, Europe's largest hedge fund manager will benefit or bear the risk of any change in the net asset value of its claims on the bank, one of the highest profile casualties of the 2007 financial crisis.
The regulatory capital impact of acquiring the exposure is expected to be about $50m and the move will have a "negligible" impact on Man's net interest expense, the group said.
"These transactions will remove the remaining uncertainty from funds with residual claims against the Lehman estates, to the benefit of both existing and new investors," Man Group Chief Executive Peter Clarke said.
"In this way, Man can use its resources productively to provide clarity for fund investors and the opportunity to grow assets in the affected funds more quickly."
The move mainly affects GLG's European Long Short and North American strategies which will share upside in "limited circumstances" in return for transferring the risk.
Directors of the relevant funds have received independent financial and legal advice with respect to the transactions, Man said.