Kim Koopersmith is taking the helm of Akin Gump Strauss Hauer & Feld — the first woman to hold the top job at one of the city’s largest law and lobbying firms.

She does so at a time the firm is changing the way it allocates and charges for legal work and is expanding its Washington office.

Akin Gump’s D.C. office houses two of three of the firm’s fastest-growing practices — international trade and public policy — and Koopersmith said she expects those two groups to continue growing as businesses increasingly look to Washington lawyers to help them navigate regulations and an overhaul of the tax code expected to surface in 2013.

“Our policy and regulatory practices are among those which most define the firm and I expect they will continue to define the firm going forward,” Koopersmith said. “As the world gets more complicated [with] the direction legislative matters take, it’s making a lot of our clients focused on our D.C.-based capabilities. There is a natural growth opportunity.”

Akin Gump has 850 attorneys worldwide, and about 260 are in Washington. The firm’s signature practice is its public policy and regulatory group, one of the most lucrative lobby shops in the city. Last year, the firm raked in nearly $38 million in lobbying revenue.

Kim Koopersmith is the first woman to lead Akin Gump.

Koopersmith is one of very few women to lead a global law firm. Only 5 percent of law firms have women in the top management position, according to a 2011 survey from the National Association of Women Lawyers, which tracks the retention and promotion of women at the nation’s 200 largest law firms.

Koopersmith, 53, is replacing Chairman Bruce McLean, who has held the post for 20 years. Koopersmith has been the firm’s U.S. managing partner since 2008, and is to become chairwoman on April 1. The firm does not plan to replace Koopersmith with a new U.S. managing partner, effectively removing one level of management for the firm’s 11 domestic offices. McLean will remain at the firm as a senior executive partner.

Koopersmith has been working closely with McLean since 2007 on succession issues, with the idea that she would eventually take over as chairwoman. She takes the reins at a time the legal industry is battling rising expenses, flat demand and growing pressure from corporate clients to offer legal services at a lower price point.

Pricing will be a major focus for the firm, said Koopersmith, who also chairs the firm’s compensation committee. Three years ago, about 10 percent of Akin Gump’s billings came from what’s known as alternative fee arrangements — ways to charge clients other than billing by the hour, such as flat fees or success fees. That has since doubled to about 20 percent, and Koopersmith said she expects that to grow.

“That is on our minds,” she said. “Reacting to the changes in the legal landscape on pricing, how we manage work and how we partner with clients ... is all different than it was 20 years ago.”

Akin Gump recently hired its first pricing director, Toby Brown, to help the firm experiment with new ways to charge for legal work and distribute work among lawyers and non-lawyers, including paralegals and researchers.

“There is a lot that can go into accomplishing client needs in a way different from the traditional model of junior associate, senior associate and partner,” she said, referring to the pyramid structure that law firms have historically used to staff legal work. “Some tasks may be done effectively by someone other than a lawyer. Or you may be able to push down [work] to more junior lawyers by training them better.”