Purification and characterization of phosphoribosylpyrophosphate synthetase from rubber tree latex

Phosphoribosylpyrophosphate synthetase (PRS; Ec 2.7.6.1) from #Hevea brasiliensis# Müll. Arg. latex was located in the cytosol. After purification, its apparent molecular weight under nondenaturing conditions was estimated at 200,000 + or - 10,000; a single band at 57,000 + or - 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 + or - 30 PM Dr adenosine triphosphate and 40 + or - 2 PM 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 vas 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 PM) and phosphoribosylpyrophosphate (inhibitor constant = 30 PM) were inhibitors. PRS responded allosterically (Hill's coefficient = 2.3) to ribulose-5-phosphate in the presence of physiological concentration of inorganic phosphate (10 mM). These results are set in the physiological context of laticifers.

Bibliographic Details

Main Authors:	Gallois, Richard, Prévôt, Jean-Claude, Clément, Anne, Jacob, Jean-Louis
Format:	article biblioteca
Language:	eng
Subjects:	F62 - Physiologie végétale - Croissance et développement, Hevea brasiliensis, latex, enzyme, pyrophosphate, purification, technique analytique, http://aims.fao.org/aos/agrovoc/c_3589, http://aims.fao.org/aos/agrovoc/c_4214, http://aims.fao.org/aos/agrovoc/c_2603, http://aims.fao.org/aos/agrovoc/c_33261, http://aims.fao.org/aos/agrovoc/c_6377, http://aims.fao.org/aos/agrovoc/c_1513,
Online Access:	http://agritrop.cirad.fr/389622/ http://agritrop.cirad.fr/389622/1/389622.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!