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Title: Slow inactivation of ribulosebisphosphate carboxylase during catalysis is not due to decarbamylation of the catalytic site

Abstract

An investigation was made of the proposal that the slow inactivation of ribulosebisphosphate carboxylase (Rubisco) activity, which occurs during in vitro assays, is due to decarbamylation of the enzyme. The level of carbamylation was compared with catalytic activity during assay conditions in which activity was both increasing and decreasing. A dual isotope procedure was used in which ({sup 3}H)carboxyarabinitol-P{sub 2} measured total active sites and {sup 14}CO{sub 2} reported the level of carbamylation. The efficacy of the procedure was verified both in the presence and in the absence of the substrate D-ribulose-1,5-bisphosphate (ribulose-P{sub 2}). These measurements showed that changes in activity during assays were not correlated with carbamylation status. Inactivation during assays initiated with both fully and partially carbamylated enzyme was not associated with any change in carbamylation level. This implies that the loss of activity during assays is not due to ribulose-P{sub 2} binding and sequestering the E form of the enzyme. Ribulose-P{sub 2} did not appear to alter the equilibrium between carbamylated and uncarbamylated enzyme, but it did slow the rate at which enzyme was both decarbamylated and carbamylated. The most likely explanation for the loss of activity during assays appears to be the sequestration of carbamylated, Mg{supmore » 2+}-bound active sites by an inhibitor.« less

Authors:
; ;  [1]
  1. Australian National Univ., Canberra (Australia)
Publication Date:
OSTI Identifier:
5962905
Resource Type:
Journal Article
Journal Name:
Plant Physiology; (USA)
Additional Journal Information:
Journal Volume: 93:4; Journal ID: ISSN 0032-0889
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CARBON-CARBON LYASES; BIOCHEMICAL REACTION KINETICS; CARBON 14 COMPOUNDS; CARBON DIOXIDE; CATALYSIS; ENZYME ACTIVITY; IN VITRO; INACTIVATION; MAGNESIUM COMPOUNDS; TRACER TECHNIQUES; TRITIUM COMPOUNDS; ALKALINE EARTH METAL COMPOUNDS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; ENZYMES; HYDROGEN COMPOUNDS; ISOTOPE APPLICATIONS; KINETICS; LABELLED COMPOUNDS; LYASES; OXIDES; OXYGEN COMPOUNDS; REACTION KINETICS; 550201* - Biochemistry- Tracer Techniques

Citation Formats

Edmondson, D L, Badger, M R, and Andrews, T J. Slow inactivation of ribulosebisphosphate carboxylase during catalysis is not due to decarbamylation of the catalytic site. United States: N. p., 1990. Web. doi:10.1104/pp.93.4.1383.
Edmondson, D L, Badger, M R, & Andrews, T J. Slow inactivation of ribulosebisphosphate carboxylase during catalysis is not due to decarbamylation of the catalytic site. United States. doi:10.1104/pp.93.4.1383.
Edmondson, D L, Badger, M R, and Andrews, T J. Wed . "Slow inactivation of ribulosebisphosphate carboxylase during catalysis is not due to decarbamylation of the catalytic site". United States. doi:10.1104/pp.93.4.1383.
@article{osti_5962905,
title = {Slow inactivation of ribulosebisphosphate carboxylase during catalysis is not due to decarbamylation of the catalytic site},
author = {Edmondson, D L and Badger, M R and Andrews, T J},
abstractNote = {An investigation was made of the proposal that the slow inactivation of ribulosebisphosphate carboxylase (Rubisco) activity, which occurs during in vitro assays, is due to decarbamylation of the enzyme. The level of carbamylation was compared with catalytic activity during assay conditions in which activity was both increasing and decreasing. A dual isotope procedure was used in which ({sup 3}H)carboxyarabinitol-P{sub 2} measured total active sites and {sup 14}CO{sub 2} reported the level of carbamylation. The efficacy of the procedure was verified both in the presence and in the absence of the substrate D-ribulose-1,5-bisphosphate (ribulose-P{sub 2}). These measurements showed that changes in activity during assays were not correlated with carbamylation status. Inactivation during assays initiated with both fully and partially carbamylated enzyme was not associated with any change in carbamylation level. This implies that the loss of activity during assays is not due to ribulose-P{sub 2} binding and sequestering the E form of the enzyme. Ribulose-P{sub 2} did not appear to alter the equilibrium between carbamylated and uncarbamylated enzyme, but it did slow the rate at which enzyme was both decarbamylated and carbamylated. The most likely explanation for the loss of activity during assays appears to be the sequestration of carbamylated, Mg{sup 2+}-bound active sites by an inhibitor.},
doi = {10.1104/pp.93.4.1383},
journal = {Plant Physiology; (USA)},
issn = {0032-0889},
number = ,
volume = 93:4,
place = {United States},
year = {1990},
month = {8}
}