Abstract
1. Glycolysis by the supernatant fraction of homogenates of liver from guinea pigs and rats at various stages of development (foetal, newborn and adult) has been examined in a suitably fortified medium by measurement of inorganic phosphate uptake and production of lactate and glycerol 1-phosphate. 2. Starting with glucose as substrate, two rate-determining steps in glycolysis occur at the stages of glucose phosphorylation and the phosphofructokinase reaction in liver tissue from animals of all ages. Effects of the post-natal development of glucokinase are recorded. 3. The appearance of microsomal glucose 6-phosphatase activity around birth has an effect on glycolysis owing to competition for glucose 6-phosphate. 4. A stimulating effect of the nuclear fraction, especially from foetal liver, on glycolysis by the supernatant fraction is interpreted as being due to stimulation by adenosine-triphosphatase activity at the 3-phosphoglycerate-kinase stage.