JPMorgan Chase & Co Chief Executive Jamie Dimon announced on Thursday that long-time colleague Jay Mandelbaum is leaving the company and that he is shifting the responsibilities of several operating executives.

Mandelbaum, 49 years-old and head of strategy and business development, "has decided to leave the firm to focus on entrepreneurial and other interests," Dimon said in a memo to employees.

"Jay has been an excellent partner of mine since 1992, and I will miss him tremendously," Dimon wrote. Mandelbaum may serve as a board member of companies in which the bank invests, Dimon said.

Dimon also said that Doug Petno, 46, has been promoted to chief executive of commercial banking and that Todd Maclin who was doing that job will now focus entirely on the consumer and business banking franchise.

In addition, John Hogan, 45, the chief risk officer of the investment bank, has been promoted to be chief risk officer for the entire company. Barry Zubrow, 58, who previously held the post, will take the new role of head of corporate and regulatory affairs.

Gordon Smith, the head of credit cards and auto lending, will now oversee three executives who previously reported to Mandelbaum and are responsible for corporate marketing, mobile and e-commerce, and the corporate internet group.

The bank is scheduled to report fourth-quarter earnings Friday.

(Reporting by David Henry; editing by Carol Bishopric)