Formate, or methanoate, is the anion derived from formic acid. Its formula is represented in various equivalent ways: CHOO− or HCOO− or HCO2−. It is the product of deprotonation of formic acid. It is the simplest carboxylate anion. A formate compound is a salt or ester of formic acid. Formate is produced in large amounts in the hepatic (liver cells) mitochondria of embryonic cells and in cancer cells by the folate cycle. Formate is reversibly oxidized by the enzyme formate dehydrogenase from Desulfovibrio gigas.