They contain nonheme iron in association with sulfur at the active site. 它们含有非血红素铁,在活性位点与硫协同作用。
Heme iron, one of two types of iron found in foods, is bound to either the blood protein hemoglobin or the muscle protein myoglobin. 食物中的两种铁的类型之一的血红素铁与血红蛋白和肌红蛋白均有关。