Abstract
1. The following aspects of energy metabolism have been compared in the erythrocytes of premature infants, full term newborn infants, and adults: levels of activity of the enzymes involved in the generation and utilization of ATP, and measurements of the content of ATP and of ADP.
2. The levels of activity of hexokinase, phosphoglyceric acid kinase and pyruvate kinase are significantly increased in the erythrocytes of premature and full term newborn infants compared to adults.
3. The level of activity of phosphofructokinase is significantly decreased in the erythrocytes of premature and full term newborn infants compared to adults.
4. In the erythrocytes of premature infants the content of ATP is significantly increased compared to both full term newborns and adults. The content of ADP is not increased. The percentage content of ADP is significantly below the values found in full term newborn infants and adults.
5. In the erythrocytes of full term newborn infants the content of both ATP and ADP is significantly greater than in adults. The ratio of ADP to the total amount of ATP plus ADP does not differ from the adult value.