Developmental changes in hepatic esterase activity towards chloramphenicol succinate and its Michaelis-Menten constant of liver, kidney and lung in human.

The hepatic esterase activities towards chloramphenicol succinate were determined in the tissues from 45 human subjects, including 18 electively aborted fetuses, 5 premature and 8 full-term newborn babies, 8 infants and 6 adults. The enzyme activities in the tissues from the fetuses and neonates were significantly lower compared with those obtained from the infants and adults. This suggests that the activity showed postnatal development. Kinetic studies of the esterase activity revealed that hepatic Km values were similar to those of the lung, but renal Km values were about 3 times higher than those of the liver and lung. In each organ, no age-related changes in Km values were observed. However, all the Vmax values in each organ showed developmental increases. Therefore, the liver plays the most important role in hydrolysis of chloramphenicol succinate when the weight of the organ is taken into consideration.