Inside the great investment houses on Wall Street, business has taken a surprising turn — downward.

Even after taxpayer bailouts restored bankers’ profits and pay, the great Wall Street money machine is decelerating. Big financial institutions, including commercial banks, are still making a lot of money. But given unease in the financial markets and the economy, brokerages and investment banks are not making nearly as much as their executives, employees and investors had hoped.

After an unusually sharp slowdown in trading this summer, analysts are rethinking their profit forecasts for 2010.

The activities at the heart of what Wall Street does — selling and trading stocks and bonds, and advising on mergers — are running at levels well below where they were at this point last year, said Meredith Whitney, a bank analyst who was among the first to warn of the subprime mortgage disaster and its impact on big banks.

Worldwide, the number of stock offerings is down 15 percent from this time last year, while bond issuance is off 25 percent, according to Capital IQ, a research firm. Based on these trends, Ms. Whitney predicts that annual revenue from Wall Street’s main businesses will drop 25 percent, to around $42 billion in 2010, from $56 billion last year.