Non reductive activation of spinach chloroplastic fructose-1,6-bisphosphatase: evidence for structural modification of the enzyme.
Preincubation of chloroplastic fructose-1,6-bisphosphatase (FBPase) in the presence of Ca2+/fructose-1,6-bisphosphate (FBS) gives rise to an active enzyme. This non-reductive activation at pH 8 occurs in the same range of time (min) as the well known reductive activation by thioredoxins and this process is reversible. A conformational change of the enzyme occurs upon the activation by Ca2+/FBP. Indeed, the circular dichroism and the fluorescence spectra of the inactive and active enzymes are different. The titration of the sulfhydryl groups of both enzymes indicates that one -SH group per monomer is unmasked upon activation, and the isoelectrofocusing pattern shows that the pI of inactive FBPase is shifted from 4.26 to 4.56 upon this non-reductive process.
Chardot
T
T
Laboratoire de Chimie biologique, Institut National Agronomique Paris-Grignon, Thiverval-Grignon, France.
Queiroz-Claret
C
C
Meunier
J C
JC
D002118:Calcium / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology*; D006597:Fructose-Bisphosphatase / Q000737:chemistry / Q000378:metabolism*; D005635:Fructosediphosphates / Q000378:metabolism; D007525:Isoelectric Focusing; D010084:Oxidation-Reduction; D010944:Plants; D011487:Protein Conformation
D005635:Fructosediphosphates; D006597:Fructose-Bisphosphatase; C029063:fructose-1,6-diphosphate; D002118:Calcium