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Medientyp:
E-Artikel
Titel:
Isolation, Identification, and Synthesis of 2-carboxyarabinitol 1-phosphate, a Diurnal Regulator of Ribulose-Bisphosphate Carboxylase Activity
Beteiligte:
Berry, Joseph A.;
Lorimer, George H.;
Pierce, John;
Seemann, Jeffrey R.;
Meek, James;
Freas, Suzan
Erschienen:
National Academy of Sciences of the United States of America, 1987
Erschienen in:
Proceedings of the National Academy of Sciences of the United States of America, 84 (1987) 3, Seite 734-738
Sprache:
Englisch
ISSN:
0027-8424
Entstehung:
Anmerkungen:
Beschreibung:
The diurnal change in activity of ribulose 1,5-bisphosphate (Rbu-1,5-P<sub>2</sub>) carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing); EC 4.1.1.39] of leaves of Phaseolus vulgaris is regulated (in part) by mechanisms that control the level of an endogenous inhibitor that binds tightly to the activated (carbamoylated) form of Rbu-1,5-P<sub>2</sub> carboxylase. This inhibitor was extracted from leaves and copurified with the Rbu-1,5-P<sub>2</sub> carboxylase of the leaves. Further purification by ion-exchange chromatography, adsorption to purified Rbu-1,5-P<sub>2</sub> carboxylase, barium precipitation, and HPLC separation yielded a phosphorylated compound that was a strong inhibitor of Rbu-1,5-P<sub>2</sub> carboxylase. The compound was analyzed by GC/MS, <sup>13</sup>C NMR, and <sup>1</sup>H NMR and shown to be 2-carboxyarabinitol 1-phosphate [(2-C-phosphohydroxymethyl)-D-ribonic acid]. Verification of structure was obtained by comparison of the inhibitory activity of the isolated compound with that of 2-carboxy-D-arabinitol 1-phosphate synthesized in vitro. This compound (but not 2-carboxy-D-arabinitol 5-phosphate) inhibited Rbu-1,5-P<sub>2</sub> carboxylase in a way that was kinetically identical to that of the isolated, naturally occurring compound. The structure of the isolated compound differs from the Rbu-1,5-P<sub>2</sub> carboxylase transition-state analogue 2-carboxyarabinitol 1,5-bisphosphate only by the lack of the C-5 phosphate group. This difference results in a higher binding constant for the monophosphate (K<sub>d</sub> = 32 nM) compared with the bisphosphate (K<sub>d</sub> < 10 pM). The less tightly bound compound acts in a light-dependent, reversible regulation of Rbu-1,5-P<sub>2</sub> carboxylase activity in vivo.