Metabolism of methionine in the newborn infant: Response to the parenteral and enteral administration of nutrients

Biju Thomas, Lourdes L. Gruca, Carole Bennett, Prabhu S. Parimi, Richard W. Hanson, Satish C. Kalhan

Research output: Contribution to journalArticlepeer-review


The rates of transmethylation and transsulfuration of methionine were quantified using [1-13C]methionine and [C2H 3]methionine tracers in newborn infants born at term gestation and in prematurely born low birth weight infants. Whole body rate of protein breakdown was also measured using [2H5]phenylalanine. The response to enteral formula feeding and parenteral nutrition was examined in full term and prematurely born babies, respectively. The relative rates of appearance of methionine and phenylalanine were comparable to the amino acid composition of mixed body proteins. Rates of transmethylation were high, both in full term infants (fast 32 ± 14 μmol kg-1·h-1; fed 21.7 ± 3.2) and in preterm infants (57.2 ± 14.8). Significant flux through the transsulfuration pathway was evident (full term: fast 6.0 ± 4.4, fed 4.1 ± 2.1; preterm: 24.9 ± 9.9 μmol kg -1·h-1). Transsulfuration of methionine is evident in the human newborn in the immediate neonatal period, suggesting that cysteine may not be considered a "conditionally" essential amino acid for the neonate. The high rate of transmethylation may reflect the high methylation demand, whereas high rates of transsulfuration in premature babies may be related to high demands for glutathione and to the amounts of methionine in parenteral amino acid mixtures.

Original languageEnglish (US)
Pages (from-to)381-386
Number of pages6
JournalPediatric research
Issue number4
StatePublished - Oct 2008
Externally publishedYes

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health


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