Lehman Brothers Holdings Inc today filed for bankruptcy protection, making it the largest casualty of the global credit crisis, and given its assets at the time of filing, Lehman surpassed WorldCom as the biggest U.S. Bankruptcy filing till date. The investment banker had close to $639 billion in assets at the time of filing, while WorldCom had about $107 billion when it did the same in 2002.

The Chapter 11 filing, however, did not include Lehman's broker-dealer operations and other units, such as asset management firm Neuberger Berman, and these will continue to operate, although Lehman is expected to liquidate them.

Lehman is among the biggest investment banks to collapse since 1990.

The Chapter 11 filing represented the end of a 158-year old company that survived world wars, the Asian financial crisis and the collapse of Long-Term Capital Management, though not the global credit crunch.

Financial institutions globally have recorded more than $500 billion of write-downs and credit losses as the U.S. subprime mortgage crisis has engulfed other markets.

Lehman had $600 billion of assets financed with just $30 billion of equity as of the end of August, which meant that a 5 percent decline in assets would wipe out the value of the company, which investors saw as a real risk thanks to the company's billions of dollars of mortgage securities.

The firm said that as of May 31, it owed about $110.5 billion on account of senior unsecured notes, about $12.6 billion on account of subordinated unsecured notes and about $5 billion on account of junior subordinated notes.

The company also disclosed that it owned stakes of 10 percent or more in a number of companies, including Imperial Sugar Co, Lpath Inc, Derma Services, Flagstone Reinsurance, GLG Partners, Ronco Corp, Pacific Energy Partners, Blount International, Pemstar Inc and Transmontaigne Inc.

The one time fourth-largest in the United States had expected to raise capital by selling off a stake in its investment unit, and use the amount as well as other funds to spin off some of its assets to shareholders.

But that plan did not satisfy investors, who pushed Lehman's share price to just a few dollars.

Lehman said the uncertainty, particularly among banks through which it clears securities trades, ultimately made it impossible for it to continue to operate.

The bankruptcy filing comes after plenty of heated negotiations among regulators and Wall Street firms about Lehman's fate. The U.S. government had refused to back Lehman's worst assets the way it did for Bear Stearns Cos Inc's sale to JPMorgan Chase.