Absence of Cystathionase in Human Fetal Liver: Is Cystine Essential?

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Science  03 Jul 1970:
Vol. 169, Issue 3940, pp. 74-76
DOI: 10.1126/science.169.3940.74


Cystathionase activity is not measurable in the livers of 24 human fetuses and 3 premature infants, and the concentration of cystathionine in the liver is higher than that of the brain. The placenta does not subserve the trans-sulfuration function. Cystine (or cysteine) thus may be an essential amino acid in the immature human.

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