Correction
| Autor: | R. Gallois, J. C. Prevot, A. Clement, J. L. Jacob |
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| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | Plant Physiology. 115:1733-1733 |
| ISSN: | 1532-2548 0032-0889 |
| DOI: | 10.1104/pp.115.4.1733 |
| Popis: | Phosphoribosylpyrophosphate synthetase (PRS; EC 2.7.6.1) from Hevea brasiliensis Mull. Arg. latex was located in the cytosol. After purification, its apparent molecular weight under nondenaturing conditions was estimated at 200,000 [plus or minus] 10,000; a single band at 57,000 [plus or minus] 3,000 was detected after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme seemed to be a homotetramer. Its affinity constants were estimated at 200 [plus or minus] 30 [mu]M for adenosine triphosphate and 40 [plus or minus] 2 [mu]M for ribose-5-phosphate. The purified enzyme proved to be functional in a paraphysiological medium (cytosol deproteinized by ultrafiltration). Optimum pH was 7.5 in buffer and 6.5 in a paraphysiological medium. No PRS activity was detected in the absence of the Mg2+ ion. Of the numerous compounds tested, only Mn2+, phosphoribosylpyrophosphate and inorganic phosphate affected the enzymatic reaction. Mn2+ (inhibitor constant = 20 [mu]M) and phosphoribosylpyrophosphate (inhibitor constant = 30 [mu]M) were inhibitors. PRS responded allosterically (Hill's coefficient = 2.3) to ribose-5-phosphate in the presence of a physiological concentration of inorganic phosphate (10 mM). These results are set in the physiological context of laticifers. |
| Databáze: | OpenAIRE |
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