His primary business is real estate, as evidenced by the under-construction Tower of Pisa. He also deals in the sale of illegal organs due to owning the Pearly Gates mortuary.
He first appears in-game working out at the gym with Candy, a personal trainer. Marcus comes in and starts to interrogate him about the Palermo Mob, but Tuzzi refuses to talk and has his goons and Candy try to kill Marcus while he leaves. His thugs are easily defeated and Candy coughs up the name of Tuzzi's accountant: Old Tony. Tony himself then states that Tuzzi has been putting all of his money into building the Tower of Pisa, with 400 luxury condo units.
Tuzzi appears to have anticipated Marcus's arrival, as he is rushing back and forth from a safe with money in an obvious attempt to escape with as much money as possible. He is not swift enough, however, as Marcus arrives and demands information. Tuzzi leaps through a window in the reception area and flees towards a lift. Candy distracts Marcus long enough for Tuzzi to reach the lift and order all of his men down to kill Marcus. He sends a group of thugs on two different floors to kill Marcus, but they fail. He eventually decides to take matters into his own hands and tries to personally kill Marcus with a crane. Marcus destroys it, however, and interrogates him. At gunpoint, Tuzzi reveals that they were paying their contact in cash at a different drop-off point every time, with the last being locker #125 at Grand Central Terminal after "El Jefe" betrayed him. With Tuzzi's arrest, the Palermo Mob finally collapsed.