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5‐Oxo‐prolinase activity in tobacco suspension cultures: Regulation by sulfate nutrition
Author(s) -
Rennenberg Heinz,
Polle Andrea,
Grundel Ina
Publication year - 1983
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1983.tb06571.x
Subject(s) - nicotiana tabacum , exponential growth , sulfate , glutathione , growth rate , sulfur , limiting , biochemistry , chloroplast , biology , chemistry , mechanical engineering , mathematical analysis , geometry , mathematics , organic chemistry , gene , engineering , enzyme
In heterotrophic and photoheterotrophic tobacco ( Nicotiana tabacum L., var. Samsun) suspensions cultured with growth‐limiting amounts of sulfate, 5‐oxo‐prolinase activity declines at the same time as the growth rate of the cells decreases. However, 5‐oxo‐prolinase activity is reduced to a greater extent than growth. As a result, the specific activity of 5‐oxo‐prolinase also declines when sulfur is scarce. The decrease in both growth and 5‐oxo‐prolinase activity can be prevented by adding sulfate to the suspensions during exponential growth. Addition of sulfate after the exponential growth phase restored neither growth nor 5‐oxo‐prolinase activity. These observations show that 5‐oxo‐prolinase activity in tobacco cells is regulated by the sulfate supply in the medium. Such a regulation is an essential prerequisite, but not a proof, for a role of 5‐oxo‐prolinase as the rate‐limiting factor in glutathione degradation. During exponential growth the average specific activity of 5‐oxo‐prolinase in heterotrophic tobacco cells is twice as high as in photoheterotrophic cells. This difference is consistent with the idea that green cells are equipped for glutathione synthesis and export, and chloroplast‐free cells for uptake and degradation of this peptide.