Aspects of amino acid metabolism in stored potato tubers (cv. Pentland Dell)

Tubers of the cv. Pentland Dell were stored at 5 and 10 degrees C for up to 33 weeks and analysed for soluble protein and free amino acids. In addition, glutamine synthetase, NADH-GOGAT and acid proteinase activities were measured over the 33-week storage period. An accumulation of asparagine and glutamine occurred during late storage which coincided with an upturn in proteinase activity. The amide content of the major tuber storage proteins suggested that amidation of free amino acids must account for the high proportion of free amides. The activities of glutamine synthetase and NADH-GOGAT further indicated amidation of free amino acids throughout storage, independent of storage temperature, An increase of total soluble protein during storage suggested that much of the observed increase in amides resulted from translocation into the tuber core tissue, perhaps as a result of the chemical suppression of sprout growth. (C) 1997 Elsevier Science Ireland Ltd.