One of Hawaii’s last venerable Big Five companies, Alexander & Baldwin Inc., could be under pressure to break itself up.

A New York hedge fund manager known to agitate for change in his investment targets bought nearly 10 percent of A&B along with a partner, it was announced yesterday. The purchase triggered expectations the 141-year-old kamaaina company will be split into pieces to elevate stock value.

Neither A&B nor the hedge funds would disclose what the intent of the A&B stock purchase — a $168 million deal — might be yesterday.

“We expect to have a constructive dialogue with them as we do with all of our shareholders,” said Suzy Hollinger, A&B’s director of investor relations.

But stock analysts with insights to A&B and people with ties to the 2,300-employee company say the play almost certainly is a breakup of the conglomerate’s three core businesses — ocean cargo transportation, commercial real estate and agriculture.

“Are the parts worth more than the whole? That’s what this comes down to,” said local stock analyst Randy Havre, echoing views of two other analysts who closely follow A&B.

Among A&B’s assets are Matson Navigation Co., 87,000 acres of land in Hawaii largely used for growing sugar cane on Maui and coffee on Kauai, and 8 million square feet of industrial, retail and office property in Hawaii and the mainland.

The breakup scenario has long been debated internally at A&B and pushed several times before by large shareholders including Hawaii stock speculator Harry Weinberg.

It’s possible the new investors have another strategy to cash in on their investment, but if the prevailing assessment from observers is accurate, splitting A&B into pieces is the objective.

Such a move faces major challenges, including a likely fight with A&B officers and board members.

The breakup of A&B would leave just one of the Big Five businesses that dominated commerce during Hawaii’s plantation era largely intact, Castle & Cooke. No longer active are the other three: Amfac, C. Brewer & Co. and TheoDavies.

Bill Ackman, the activist hedge fund manager running Per­shing Square Capital Management LP, is in the position to exert the most shareholder influence over A&B’s future. Affiliates of his New York-based firm bought 8.6 percent of A&B stock for $148 million.

San Francisco-based Marcato Capital Management LLC, led by former Per­shing Square partner Richard Mc­Guire, acquired a

1.3 percent stake for about $21 million.

The two firms, which disclosed their purchases in a joint regulatory filing yesterday, are now A&B’s largest shareholder. A&B has several other large shareholders with individual stakes close to 5 percent, but they are traditionally passive investors.

Calls seeking comment from the Ackman and Mc­Guire firms were not returned yesterday. In the regulatory filing, the firms said they plan to hold discussions with A&B management, directors, other stockholders and other parties “concerning the business, assets, capitalization, financial condition, operations, governance, strategy and future plans” of the company.

The firms said in the filing that they believe A&B shares are undervalued and are an attractive investment.

A&B shares recently had been trading close to a 52-week high, and closed yesterday at $45.65. Disclosure of the Ackman and Mc­Guire purchases after the stock market closed yesterday helped push A&B stock as high as $50.88 in after-hours trading. The firms accumulated A&B stock over a recent period for $41.04 a share on average.

Ackman, who controls a $9 billion fund, is known for making big investments in companies he deems undervalued and urging changes he believes will boost shareholder returns.

Investments by Ackman include a recent deal that pushed a breakup plan for Illinois-based Fortune Brands Inc., the maker of Jim Beam bourbon, Titleist golf equipment, Moen faucets and Master Lock padlocks.

Ackman viewed Fortune Brands as a piggy bank in need of a hammer, according to a February story in Bloomberg Businessweek. Fortune Brands endorsed the breakup, and Ackman’s 11 percent investment in the company has grown by $320 million.

Ackman also attempted to get retail giant Target to sell the real estate under its stores, but he was unsuccessful after a contentious battle.

The investor also was a major influence in mall and property owner General Growth Properties filing for bankruptcy and spinning off major real estate assets into a new company, Howard Hughes Corp. Ackman is now chairman of Hughes Corp., which owns, among other assets, Ward Centers in Hono­lulu.

Ackman has made other investments that did not focus on carving up company assets.

The financial track rec­ord of Ackman is hugely positive, though investments in some companies including Target and Borders didn’t turn out well.

According to the Bloomberg Businessweek article, Ackman rarely gives up on his initiatives. In the Target case his bid to influence the retailer included a $10 million campaign complete with TV ads aimed at getting himself and four allies elected to the board. Ackman did not gain the board seats.

Local analyst Havre said there is no doubt Ackman will seek a seat or seats on A&B’s board, asking, “He’s got a big investment, why shouldn’t he have some representation on the board?”

Ackman recently landed a seat on the board of J.C. Penney Co. after buying up shares of the department store chain. But some observers suggest that Ackman might have a tough time getting on the board of A&B, a company largely controlled by local business executives already trying to deliver the best return to shareholders.

John Couch, a former A&B chairman and CEO, said hedge fund managers might believe they have better ideas for running companies based on research. But in Couch’s view, A&B has a long-term history of good performance and leadership.

“These (A&B leaders) aren’t guys that have just fallen off the papaya truck,” he said.

At the same time, Couch said breaking up A&B has previously been, and will continue to be, an area for debate with valid arguments for and against such a move.