HOUSTON -- Two former Enron executives whose cooperation with prosecutors helped bring convictions for the architects of the biggest scandal in U.S. corporate history received sharply reduced sentences Friday.

Michael Kopper, once the top lieutenant to former Enron Chief Financial Officer Andrew Fastow was sentenced to three years and one month in prison. An hour later, Mark Koenig, the company's former investor relations chief, received an 18-month sentence.

Prosecutors had asked U.S. District Judge Ewing Werlein Jr. to sharply cut the sentences for Kopper and Koenig because of their cooperation.

Kopper, 41, was the first former Enron executive to plead guilty to charges stemming from the company's collapse and faced up to 15 years in prison. Koenig, 51, who helped present the company's false financial reports to investors, pleaded guilty in August 2004 to one count of aiding and abetting securities fraud, which carries up to 10 years in prison.

Kopper led federal prosecutors to Fastow, who in turn led them to Enron founder Kenneth Lay and former Chief Executive Jeffrey Skilling.

Fastow just began serving six years in a federal prison in Louisiana, while Skilling will begin serving a sentence of more than 24 years next month at a low-security prison in Minnesota. Lay's conviction for conspiracy, fraud and other charges were wiped out with his death in July from heart disease.

Earlier this week, Richard Causey, the company's former chief accounting officer, was sentenced to 5 1/2 years for his role in the company's collapse.

Kopper pleaded guilty in 2002 to money laundering and conspiracy to commit wire fraud. He also surrendered nearly $12 million in ill-gotten gains.

Prosecutors said that from May 1997 through September 2001, Kopper took advantage of off-balance-sheet partnerships and accounting methods to funnel millions of dollars to himself, Fastow and others at the expense of the company and its shareholders.

Ruemmler said Koenig warranted a substantial reduction in his sentence because his assistance resulted in the guilty pleas of other Enron executives and contributed to the successful prosecution of Lay and Skilling.

"Perhaps more significantly, however, Mr. Koenig has embraced the spirit of full cooperation through his genuine remorse, his commitment to the truth and his efforts to right his wrongs through his actions," Ruemmler wrote in another court filing this week.

Koenig was the government's first witness in Lay and Skilling's trial earlier this year.

During his seven days on the stand, Koenig told jurors that Enron, bent on matching or beating Wall Street expectations, fudged its earnings figures with the knowledge of Skilling and Lay.

In his role, Koenig worked with both men, serving as the company's main link to investors and analysts. He coordinated analyst presentations and oversaw the company's earnings announcements.

Enron, once the nation's seventh-largest company, crumbled into bankruptcy proceedings in December 2001 after years of accounting tricks could no longer hide billions in debt or make failing ventures appear profitable. The collapse wiped out thousands of jobs, more than $60 billion in market value and more than $2 billion in pension plans.