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Main Title: Competition of Pyridoxal 5'-Phosphate with Ribulose 1,5-Bisphosphate and Effector Sugar Phosphates at the Reaction Centers of the Spinach Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase
Author(s): Vater, Joachim
Gaudszun, Thomas
Scharnow, Harald
Salnikow, Johann
Type: Article
Language Code: en
Abstract: The Stimulation of the carboxylase reaction by effectors of ribulose 1,5-bisphosphate carboxyl­ ase/oxygenase displays higher sensitivity towards pyridoxal 5'-phosphate inhibition than the catalytical process itself. Pyridoxal 5'-phosphate binding to the enzyme is not affected by the modulators 6-phospho-gluconate and fructose 1,6-bisphosphate at low concentrations at which these agents stimulate the carboxylation rate. At higher concentrations these sugar phosphates protect the enzyme against pyridoxal 5'-phos-phate inhibition in a similar fashion like the substrate ribulose 1,5-bisphosphate. Such protection experiments in combination with spectrophotometrical studies of pyridoxal 5'-phosphate binding demonstrate two binding states of ribulose 1,5-bisphosphate at the reaction centers of the enzyme with different requirements for Mg2+. 6-Phosphogluconate functions as protector only in the presence of Mg2+. Our results imply a competition between pyridoxal 5'-phosphate and substrate or effector sugar phosphates at the reaction centers of the spinach carboxylase. It is proposed that the pyridoxal 5'-phosphate inhibition of the stimulatory activity of these effectors originates from a modification of the regulatory sites of the enzyme caused by pyridoxal 5'-phosphate binding to the catalytical sites.
Issue Date: 1980
Date Available: 4-Jan-2019
DDC Class: 570 Biowissenschaften; Biologie
Subject(s): ribulose 1,5-bisphosphate carboxylase/oxygenase
effector studies
pyridoxal 5'-phosphate inhibition
Journal Title: Zeitschrift für Naturforschung C
Publisher: De Gruyter
Publisher Place: Berlin
Volume: 35
Issue: 5-6
Publisher DOI: 10.1515/znc-1980-5-611
Page Start: 416
Page End: 422
EISSN: 1865-7125
ISSN: 0939-5075
Appears in Collections:FG Physikalische Chemie / Biophysikalische Chemie » Publications

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