Kenneth Berman, associate director of the SECs division of investment management, is stepping down after 12 years to become a partner with the law firm of Debevoise & Plimpton. Mr. Berman, associate director since 1997, will leave at the end of August. In a statement, Paul Roye, SEC investment management director, called Mr. Bermans departure a substantial loss. Mr. Berman supervised a range of activities relating to investment company regulation and played a key role in the administration of the Public Utility Holding Company Act of 1935. A successor has not been named, said Carol Patterson, SEC spokeswoman.