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Possible Polypeptide Synthesis Following Injection of Balanced but Incomplete Amino Acid Mixes into Lizards¹

Department of Biochemistry, Louisiana State University Medical Center, New Orleans, LA 70119

The rate of disappearance of carcass-free amino acids following an injection of a mixture of the composition of fish muscle was compared with the rate seen after giving the same mix minus three essential amino acids in one series of experiments, and minus five amino acids in another series. The experimental animal was a 3.5 g lizard (Anolis carolinensis) whose metabolic rate is about equal to man's. Lizards were injected with one of the mixes, at intervals some were killed and homogenized, and the free amino acids were assayed on protein-free filtrates of the entire carcass. Amino acids disappeared from complete and incomplete mixes at the same rate, a rate several-fold greater than that at which they could be catabolized. When three or five essential amino aids (as defined for the growing rat) were injected by themsleves, they were removed only one-third as fast as when accompanied by a balanced mix of the rest of the protein components. I concluded that if the amino acids were in proper ratio and if they were sufficient in number, they were removed rapidly even though as many as five essential amino acids are missing. For want of a better explanation, some type of macromolecule synthesis from balanced incomplete mixes was postulated.

KEY WORDS: • lizards • amino acid metabolism

¹ Supported in part by the Louisiana Department of Wildlife and Fisheries.

Manuscript received 24 October 1980.