The Volcker Rule, a proposal approved by U.S. regulators on Tuesday that would restrict Wall Street's ability to trade for its own profit, could lower fixed income revenues significantly and affect the largest U.S. banks, one analyst said.

"It looks like based on the summaries that we're seen and what we've read in it that they're really trying to shut down flow trading [see definition below], which is really core to how fixed income operates," said Brad Hintz, a senior analyst at Sanford C. Bernstein.