Channeling of the intermediates and catalytic facilitation to Rubisco in a multienzyme complex of Calvin cycle enzymes.
Indian J Biochem Biophys
;
1994 Aug; 31(4): 215-20
Article
in English
| IMSEAR
| ID: sea-27990
ABSTRACT
Calvin cycle multienzyme complex, consisting of phosphoriboisomerase, phosphoribulokinase and ribulose-1,5-bisphosphate carboxylase (Rubisco), shows ribose-5-phosphate + ATP dependent CO2 fixation activity with a small but discernible lag. Transient time analysis showed that the lag at pH 7 was independent of multienzyme concentration and was significantly lower than the expected transient time calculated from Km and Vmax of the individual enzymes, indicative of channeling of the intermediates in the enzyme complex. Channeling of ribulose-1,5-bisphosphate was found to offer a catalytic advantage to Rubisco. Rubisco shows a decrease in activity during catalysis in ribulose-1,5-bisphosphate dependent CO2 fixation reaction, due to the formation of the catalytic inhibitor. Such a decrease of Rubisco activity was not observed in ribose-5-phosphate + ATP dependent CO2 fixation reaction and the catalytic inhibitor was also not detected. These results suggested that the intermediates are channeled in the complex and channeling offers a catalytic facilitation to Rubisco.
Full text:
Available
Index:
IMSEAR (South-East Asia)
Main subject:
Ribulose-Bisphosphate Carboxylase
/
Carbohydrate Epimerases
/
Catalysis
/
Phosphotransferases (Alcohol Group Acceptor)
/
Spinacia oleracea
/
Plant Leaves
/
Aldose-Ketose Isomerases
/
Multienzyme Complexes
Language:
English
Journal:
Indian J Biochem Biophys
Year:
1994
Type:
Article
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