Hysteresis and Reversible Cold-Inactivation of ADP-Glucose Pyrophosphorylase From Barley Seeds
| Autor: | Leszek A. Kleczkowski, Odd-Arne Olsen, Per Villand |
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| Rok vydání: | 1993 |
| Předmět: | |
| Zdroj: | Zeitschrift für Naturforschung C. 48:457-460 |
| ISSN: | 1865-7125 0939-5075 |
| Popis: | ADP-glucose pyrophosphorylase (AGP) from barley (Hordeum vulgare L.) seed endosperm showed a lag in activity when assayed after storage at -20 °C. The cold-stored enzyme could regain most, or all, of its activity during 40-60 min following exposure to ambient temperatures. The lags were not observed when 2 mM MgCl2 was added to the storage buffer before freezing. Storage at -20 °C, in the absence of MgCl2, led to the appearance of a low activity A GP form which was activated up to 3-fold by 3-phosphoglycerate (PGA) and had high Km values with ATP of 0.3 and 1.2 mM (with and without PGA, respectively). In contrast, storage at -20 °C in the presence of MgCl2 or incubation at +20 °C resulted in an active enzyme which was only weakly activated by PGA (up to 30%) and had the respective Km values with ATP of 0.1 and 0.3 mM . It is suggested that low temperature may induce a change in the conformation and/or oligomerization state of the AGP protein, resulting in a low activity enzyme form which has distinct regulatory and kinetic properties. |
| Databáze: | OpenAIRE |
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