Subsaturating ribulose-1,5-bisphosphate concentration promotes inactivation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco): studies using continuous substrates addition in the presence and absence of Rubisco activase

We developed a continuous-addition method for maintaining subsaturating concentrations of ribulose-1,5-bisphosphate (RuBP) for several minutes, while simultaneously monitoring its consumption by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This method enabled us to observe the effects...

Full description

Saved in:
Bibliographic Details
Published inPlant physiology (Bethesda) Vol. 109; no. 4
Main Authors Portis, A.R. Jr. (Australian National University, Canberra, Australia.), Lilley, R.M, Andrews, T.J
Format Journal Article
LanguageEnglish
Published 01.12.1995
Subjects
ACTIVIDAD ENZIMATICA
ACTIVITE ENZYMATIQUE
AZUCARES FOSFATOS
DIOXIDO DE CARBONO
DIOXYDE DE CARBONE
DURACION
DUREE
ESTRUCTURA QUIMICA
MEDIO DE CULTIVO
MILIEU DE CULTURE
NICOTIANA TABACUM
RUBISCO
SPINACIA
STRUCTURE CHIMIQUE
SUCRE PHOSPHATE
Online AccessGet full text

Cover

More Information
Summary:We developed a continuous-addition method for maintaining subsaturating concentrations of ribulose-1,5-bisphosphate (RuBP) for several minutes, while simultaneously monitoring its consumption by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This method enabled us to observe the effects of subsaturating RuBP and CO2 concentrations on the activity of Rubisco during much longer periods than previously studied. At saturating CO2, the activity of the enzyme declined faster when RuBP was maintained at concentrations near its Km value than when RuBP was saturating. At saturating RuBP, activity declined faster at limiting than at saturating CO2, in accordance with previous observations. The most rapid decline in activity occurred when both CO2 and RuBP concentrations were subsaturating. The activity loss was accompanied by decarbamylation of the enzyme, even though the enzyme was maintained at the same CO2 concentration before and after exposure to RuBP. Rubisco activase ameliorated the decline in activity at subsaturating CO2 and RuBP concentrations. The results are consistent with a proposed mechanism for regulating the carbamylation of Rubisco, which postulates that Rubisco activase counteracts Rubisco's unfavorable carbamylation equilibrium in the presence of RuBP by accelerating, in an ATP-dependent manner, the release of RuBP from its complex with uncarbamylated sites
Bibliography:F60
9716125
ISSN:0032-0889
1532-2548