Differences in liver folate enzyme patterns in premature and full term infants.

The specific activities of four folate enzymes have been measured in livers from preterm infants (Group 1), full-term infants (Group 2), and from control subjects (Group 3). The four enzymes studied were methylene tetrahydrofolate reductase (EC 1.1.1.68), methionine synthetase (EC 2.1.1.13), methylenetetrahydrofolate dehydrogenase (EC 1.5.1.5), and glutamate formiminotransferase (EC 2.1.2.5). The specific activities for methylenetetrahydrofolate reductase were 6.62 +/- 0.51, 4.42 +/- 0.31, and 2.60 +/- 0.40 (nmoles formaldehyde/mg protein/h, mean +/- S.E.) for groups 1, 2 and 3, respectively. The specific activities for the three groups for methionine synthetase were 0.99 +/0 0.11, 0.64 +/- 0.06, and 0.42 +/- 0.05 (nmoles methionine/mg protein/h), mean +/- S.E.). The specific activities for the three groups for glutamine formiminotransferase were 84.1 +/-10.7, 108.6 +/-14.6, and 104.3 +/- 17.8 (nmoles methenyltetrahydrofolate/mg protein/min, mean +/- S.E.). The specific activities for the three groups for methylenetetrahydrofolate dehydrogenase were 0.16 +/- 0.03, 0.39 +/- 0.07, and 0.92 +/- 0.16 (nmoles methenyltetrahydrofolate/mg protein/min, mean +/- S.E.). During development, the specific activities of methylenetetrahydrofolate reductase and methionine synthetase decreased whereas the specific activity of methylenetetrahydrofolate dehydrogenase increased and that of glutamate formiminotransferase remained constant. In addition, the activities of methylenetetrahydrofolate reductase, methionine synthetase, and methylenetetrahydrofolate dehydrogenase were significantly influenced by postnatal age.