Infancy Protein intake

Ornithine carbamoyltransferase (ornithine transcar-bamylase) (EC 2.1.3.3). Gross elevation of blood ammonia. Elevated glutamine in plasma and cerebrospinal fluid. Urea excretion low. Urinary orotic add increased. Uracil and uridine in urine. Gene for enzyme X-linked. Condition severe in boys (0-0.2% of normal enzyme activity in liver), who die in postnatal period (some cases of late onset have been reported). Girls have 5-10% normal liver enzyme activity. Some girls have died in late infancy or childhood, and others have survived with restricted protein intake. Abnormal EEC, mental retardation, brain atrophy and hepatomegaly. 

The importance of proper nutrition during infancy is illustrated by the infant s nutritional requirement. On a body weight basis, the infant requires far more essential amino acids than the adult. The infant must receive histidine, which is not essential in the adult diet. The 2-month-old premature infant and the 3-month-old term infant may require as much as 8 mg of iron a day. Such an amount is usually not found in the diet, and supplementation is necessary. An adequate protein intake is necessary for the maintenance of health in the infant and growing child, but the exact protein requirement is not known. 

For individuals who do not respond to Bg, a methionine-restricted diet is necessary (Box 14.4). Synthetic methionine-free amino acid medical foods are commercially available. The natural requirement for methionine is met by dietary intake of regular foods or, in infancy, standard infant formulas. The diet is restrictive and requires the use of low-protein products to be truly successful. Cystine is prescribed as necessary to obtain normal cysteine concentrations. Small amounts of vitamin B12 may aid in the remethyl-ation of homocysteine to methionine due to its use as a cofactor by methionine synthase [10,40]. 

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