It is found in the enzyme cytochrome c oxidase, which is part of the respiratory electron-transport chain, and in the protein plastocyanin, which is involved in photosynthetic electron transport.

• 存在于细胞色素c氧化酶中，该酶是呼吸电子传递链上的一个部分。它还存在于质体蓝素蛋白中，和光合电子传递有关。