The holding companies of Professional Business Bank and Bank of Manhattan on Tuesday announced that they would merge in a stock transaction creating a combined bank with assets of more than $406 million.

Manhattan Bancorp, the El Segundo parent of Bank of Manhattan, will be the surviving holding company, a spokesman said, although shareholders of Pasadena’s CGB Holdings, PBB’s holding company, would own more than half of the combined entity.

Terry Robinson, president and chief executive of Bank of Manhattan, will serve as chief executive of the new bank. John Nerland, president and chief banking officer of PBB, will be president.

“The union of these two Los Angeles banks creates a stronger commercial bank with which to serve small business growth in the Southland and to support continued growth in our mortgage operations,” said Robinson in a statement.

The deal appears to provide an exit for PBB Chief Executive Mary Lynn Lenz, who joined the then financially troubled bank in 2009 and helped engineer a capital-boosting merger with California General Bank that closed in January.

Carpenter Community BancFunds, CGB Holdings’ sole owner, invested additional capital in conjunction with the January merger. The funds, controlled by Irvine investment banker and consultant Ed Carpenter’s Carpenter & Co., also have a significant stake in Manhattan and will have a big stake in the post-merger Manhattan Bancorp.

As of Sept. 30, PBB had assets of more than $259 million and deposits of $212 million, while Manhattan Bancorp and Bank of Manhattan had combined assets of nearly $147 million and deposits of more than $111 million.

Pending regulatory approvals, the merger is expected to close in the first quarter of next year. Shares of Manhattan Bancorp will continue to trade on the Over-the-Counter Bulletin Board after the merger, the spokesman said. CGB Holdings shares do not trade publically.

Manhattan Bancorp shares were down 15 cents, or 7 percent, to $2 in midday trading.