Age-induced protein modifications and increased proteolysis in potato seed-tubers
- Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Agricultural, Food and Nutritional Science
- Univ. of Kentucky, Lexington, KY (United States). Dept. of Horticulture and Landscape Architecture
Long-term aging of potato (Solanum tuberosum) seed-tubers resulted in a loss of patatin and a cysteine-proteinase inhibitor, potato multicystatin (PMC), as well as in increase in the activities of 84-, 95-, and 125-kD proteinases. Highly active, additional proteinases appeared in the oldest tubers. Over 90% of the total proteolytic activity in aged tubers was sensitive to trans-epoxysuccinyl-L-leucylamido (4-guanidino) butane or leupeptin, whereas pepstatin was the most effective inhibitor of proteinases in young tubers. Proteinases in aged tubers were also inhibited by crude extracts or purified PMC from young tubers, suggesting that the loss of PMC was responsible for the age-induced increase in proteinase activity. Nonenzymatic oxidation, glycation, and deamidation of proteins were enhanced by aging. Aged tubers developed daughter tubers that contained 3-fold more protein than mother tubers, with a polypeptide profile consistent with that of young tubers. Although PMC and patatin were absent from the older mother tubers, both proteins were expressed in the daughter tubers, indicating that aging did not compromise the efficacy of genes encoding PMC and patatin. Unlike the mother tubers, proteinase activity in daughter tubers was undetectable. Their results indicate that tuber aging nonenzymatically modifies proteins, which enhances their susceptibility to breakdown; the authors also identify a role for PMC in regulating protein turnover in potato tubers.
- Sponsoring Organization:
- Natural Sciences and Engineering Research Council of Canada, Ottawa, ON (Canada); USDOE, Washington, DC (United States)
- OSTI ID:
- 305471
- Journal Information:
- Plant Physiology (Bethesda), Vol. 119, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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