Regulation of Glyconeogenesis from Amino Acids by Acetate in Tetrahymena pyriformis

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Abstract
The regulation of glyconeogenesis from amino acids by acetate was studied in Tetrahymena pyriformis. Alanine aminotransferase and glutamate dehydrogenase were repressed by 0.1% sodium acetate in the growth medium. Incorporations into the glycogen of washed cells from the respective isotopically labelled amino acids were similarly suppressed.Incorporations into glycogen from uniformly 14C-labelled L-serine, L-leucine, L-isoleucine, L-tyrosine, and DL-β-14C-tyrosine were also suppressed by prior growth in a medium supplemented with 0.1% or 0.3% acetate. Percentage incorporation into glycogen was highest from tyrosine, followed by leucine, isoleucine, and alanine, and lowest from glutamic acid and serine.Supplementation of the medium with 0.25% glucose resulted in repression of the above two enzymes and suppression of incorporation into glycogen from amino acids.Incorporation of aspartic acid into glycogen was negligible and was variously and minimally affected by growth in glucose- or acetate-supplemented media. Aspartate aminotransferase was affected in a like manner.Glycogen content was not significantly affected by growth in media supplemented with 0.1% or 0.3% acetate. On the whole, the data suggest that acetate spares amino acids for glyconeogenesis by a mechanism which entails repression of amino-acid-catabolizing enzymes.

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