ABSTRACT
Free amino acids in embryos and larvae of Xenopus laevis have been studied chromatographically. Quantitative measurements have been made on eight amino acids, and their concentrations have been compared between different regions of the embryo and between different tissues of the larva.
Extracts of whole embryos showed higher concentrations of free aspartic acid and glutamic acid in the morula than in the early gastrula; significantly more leucine in the late gastrula than in the early gastrula, and less glutamine in the neurula than in the early tailbud.
A number of free amino acids were more highly concentrated in the dorsal lip than in other parts of the early gastrula. Differences were also apparent between dorsal and ventral halves of the neurula, early tailbud stage, and hatched larva. In the early tailbud stage there was more glutamine in the head than in other regions and a higher percentage of glycine in the trunk.
The main features of the free amino-acid concentrations in larval brain, eyes, somites, heart, liver, and skin are described and compared. In some features the free amino-acid concentrations in embryonic tissues resemble those of the larval tissues that derive from them in development.
The evidence for special functions of certain amino acids in morphogenesis and in the synthesis of specific proteins is discussed.