Searching for new ideas for your portfolio? Take a look at what company insiders are doing. Company executives, board members, and shareholders with stakes exceeding 10% must notify the SEC within two days of their share purchases (and sales) in a Form 4 filing.

Insider buying can be a bullish indicator for a stock and provides another piece of information for investors to weigh when doing research. So let's take a look at where insiders were stepping up to the plate over the past week.

Company Name Market Cap Number of  Shares Purchased $Value Shares Purchased CAPS Rating (out of 5)
TransAtlantic Petroleum (AMEX: TAT) $1.02 billion 1,788,640 $5.01 million ****
Enstar Group (Nasdaq: ESGR) $1.06 billion 65,000 $4.55 million *****

Lawson Software

(Nasdaq: LWSN)

$1.41 billion 528,000 $4.31 million ****
Valence Technology (Nasdaq: VLNC) $162 million 1,923,000 $2.0 million **

Sources: Barron's; Yahoo! Finance; Motley Fool CAPS.

Oil and gas exploration and production company TransAtlantic Petroleum has properties in Turkey, Morocco, and California. Chairman N. Malone Mitchell 3d participated in a public offering of TransAtlantic's shares at $2.80 apiece. TransAtlantic also has a line of credit with Mitchell's investment fund, Dalea Partners, which was used to finance its acquisition of Amity Oil, a Turkish exploration and production company, giving the company more exposure to Turkey and Mitchell more exposure to the company's performance.

At Enstar Group, director Charles Akre's investment firm, Akre Capital Management, bought shares. It owns nearly 3% of the company. For nearly 13 years, Akre was portfolio manager of the FBR Focus Fund. On the same day Akre bought, the company's CEO and co-chief operating officers sold shares, though the CEO's selling was motivated by taxes.

Investor Carl Icahn bought more shares in Lawson Software, an enterprise software company. Icahn disclosed an 8.5% stake in the company back in May, and his recent purchase takes his stake in the company above the 10% mark. With an ownership stake of this size, expect Icahn to be noisy about what he wants management to do to boost the company's share price. Given the consolidation in the enterprise software space, don't be surprised if Icahn wants the company to become a takeover target. Analysts see Oracle (Nasdaq: ORCL), SAP (NYSE: SAP), and IBM (NYSE: IBM) as potential buyers.

Carl Berg, founder and chairman of the lithium ion battery company Valence Technology, invested $2 million in the company. While the company continues to lose money, recent deals to supply batteries for Wrightbus, a U.K. maker of hybrid buses, and Smith Electric, a maker of electric commercial trucks, should move it closer to profitability.

While Fools should do their own due diligence, and not blindly follow the insiders, insider buying can point to good places to look for opportunities. If I had to place bets on this week's list, my money would be on Lawson Software, given Icahn's reputation and track record.

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