specific and only acts on SEPHCHC and close derivatives. Controversy MenH (SHCHC synthase) was previously thought to be a thioesterase involved in hydrolyzing DHNA-CoA in a later step of menaquinone synthesis. In 2008, it was determined that MenH has poor catalytic activity toward palmitoyl-CoA, casting doubt on its role as a thioesterase. Direct analysis confirmed that MenH is unable to hydrolyze DHNA-CoA. In 2009, it was proposed that a dedicated hotdog fold thioesterase would be needed to catalyze the hydrolysis of DHNA-CoA. A protein was identified in 2013 that could fit this role. References EC 4.2.99 Enzymes of known structure