GlaxoSmithKline announced this evening that it would shift its toothpaste manufacturing from New Jersey to Greene County preventing the shutdown of its plant in Oak Hill. The British pharmaceutical giant had planned to shutter the Oak Hill plant by 2012, following its $3.6 billion acquisition last year of Stiefel Laboratories, which made skin products there. Glaxo will still shift skin-product manufacturing to a plant in Canada, as originally planned. But it will invest $56 million to remake the Oak Hill factory to manufacture Aquafresh, the company and Greene County officials said. The move will not save every Glaxo job in Greene County. After the transition, the Oak Hill plant will employ about 200 workers, down from the more than 260 who work there now. And some of the jobs will be taken by workers transferring from the plant in Clifton, N.J., which will close in 2012. “It’s going to be a mix and match of current employees and new employees,” said Alexander “Sandy” Mathes, the executive director of the Greene County Industrial Development Agency, which worked to save the plant. Glaxo’s decision to close the plant stunned Greene County officials, who have depended on the factory as a stable source of employment in the mostly rural area. Officials described Thursdays announcement as a victory resulting from a long effort by several local and state agencies including Empire State Development, the Division of Housing and Community Renewal and others to keep the factory open. In part, they did that by targeting the factory for nearly $7 million in grants designed to boost energy efficiency and modernize the plant. Also, the Greene County IDA will freeze property taxes at the site and exempt Glaxo from some sales taxes. The Oak Hill plant consists of 250,000 square feet of manufacturing and laboratory space along Route 145.