Absence of cystathionase in human fetal liver: is cystine essential?
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.
D000596:Amino Acids / Q000378:metabolism*; D001921:Brain / Q000196:embryology / Q000201:enzymology; D003553:Cystine / Q000378:metabolism*; D004044:Dietary Proteins; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006710:Homocysteine / Q000378:metabolism; D006801:Humans; D006836:Hydro-Lyases / Q000378:metabolism*; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007234:Infant, Premature; D008099:Liver / Q000196:embryology / Q000201:enzymology* / Q000378:metabolism*; D008715:Methionine / Q000097:blood; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D014166:Transferases / Q000378:metabolism
D000596:Amino Acids; D004044:Dietary Proteins; D006710:Homocysteine; D003553:Cystine; D008715:Methionine; D014166:Transferases; D006836:Hydro-Lyases