The development of cystathionase activity during the first year of life.

The development of hepatic cystathionase (EC 4.4.1.1) activity is dependent both upon the gestational age of the infant and the postnatal age. Full-term infants are born with greater hepatic cystathionase activity than pre-term infants, and the activity increases rapidly after birth reaching mature levels at about 3 months of age. Prematurely born infants have lower hepatic cystathionase activity at birth and like the full-term, the activity increases after birth. Cystathionase activity is not isolated to the liver. In both premature and full-term infants, it is present in the kidneys, and adrenals, but of little significance in the pancreas. These in vitro measurements of cystathionase activity indicate that the premature infant is potentially capable of endogenous cysteine production if provided with adequate methionine.