The Entner-Doudoroff pathway is a glycolytic pathway that is considered the second pathway used for carbohydrates used by certain microbes. In this process, glucose-6-phosphate is oxidized through 6-phosphogluconate to pyruvate and glyceraldehyde 3-phosphate, with the concomitant reduction of NADP. By conventional glyceraldehyde-3-phosphate oxidation to pyruvate, one NAD is reduced and a net one ATP is formed. In that pathway, for every glucose molecule there is an "investment" of one ATP molecule and a yield of two ATP and two pyruvate molecules and one NADH. The difference between the glycolytic used by humans and this pathway is that the latter requires one ATP to yield two ATP and two pyruvates as a net of only one NADPH produced and one ATP result (from substrate-level phosphorylation), and the former requires two ATP molecules to yield four ATP and two pyruvate molecules per glucose as a net of two ATP molecules.