Oxidation of glyceraldehyde 3-phosphate The conversion of glyceraldehyde 3-phosphate to 1,3-bisphospho- glycerate by glyceraldehyde 3-phosphate dehydrogenase is the first oxidation-reduction reaction of glycolysis (Figure 8.18). [Note: Because there is only a limited amount of NAD + in the cell, the NADH formed by this reaction must be reoxidized to NAD + for gly- colysis to continue. Two major mechanisms for oxidizing NADH are: 1) the NADH-linked conversion of pyruvate to lactate (anaerobic, see p. 96), and 2) oxidation of NADH via the respiratory chain (aero- bic, see p. 75). The latter requires substrate shuttles (see p. 79.]