Brent rescued Argyle from administration in October 2011 following back-to-back relegations, which had left the club in League Two.
Former director and ex-Waitrose managing director David Felwick has returned to the Pilgrims' board and will become the club's new chairman.
US-based director Simon Hallett has bought shares from Brent to take over as the club's majority shareholder, while the incumbent chairman will remain as a non-executive director.
"It has been an incredible privilege to lead Argyle's board as custodians of our club over the last seven years. It's now time for the next exciting chapter to begin," Brent said in a statement.
"I'd like to thank Simon and [his wife] Jane for their considerable financial commitment, which unlocks huge opportunities for the club and wider community."
The Pilgrims will also enter a conditional contract to buy land adjacent to Home Park which is not needed for a planned new ice arena.