Abstract
Summary
The phenylalanine-hydroxylating system of chick liver was found to resemble the mammalian liver system in characteristics and components, with apparent involvement of a phenylalanine hydroxylase, a pteridine cofactor and a cofactor reductase. Studies on the pattern of appearance of the avian liver system during embryonic and post-hatching development of the chick showed that the activity rises from a low level in early embryo to a peak shortly before hatching, in apparent contrast to the developmental pattern reported for the mammalian system. Also in apparent contrast to recent studies on the mammalian system, the limiting factor primarily responsible for the pattern of development in avian liver appeared to be a relative lack of active phenylalanine hydroxylase component in the early chick embryo.
The authors wish to acknowledge the technical assistance of Mr. Ernest Jones and Mr. Walter Wiley.
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