Thermodynamic analysis of the emergence of new regulatory properties in a phosphoribulokinase-glyceraldehyde 3-phosphate dehydrogenase complex.
Glyceraldehyde 3-phosphate dehydrogenase and phosphoribulokinase exist as stable enzymes and as part of a complex in Chlamydomonas reinhardtii. We show here that phosphoribulokinase exerts an imprinting on glyceraldehyde 3-phosphate dehydrogenase, which affects its catalysis by decreasing the energy barrier of the reactions with NADH or NADPH by 3.8 +/- 0.5 and 1.3 +/- 0.3 kJ.mol(-1). Phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase within the complex are regulated by NADP(H) but not by NAD(H). The activities of the metastable phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase released from the complex preincubated with NADP(H) are different from those of the metastable enzymes released from the untreated complex. NADP(H) increases phosphoribulokinase and NADPH-glyceraldehyde 3-phosphate dehydrogenase activities with a (~)K(0.5 (NADP)) of 0.68 +/- 0.16 mm and a (~)K(0.5 (NADPH)) of 2.93 +/- 0.87 mm and decreases NADH-dependent activity. 1 mm NADP increases the energy barrier of the NADH-glyceraldehyde 3-phosphate dehydrogenase-dependent reaction by 1.8 +/- 0.2 kJ.mol(-1) and decreases that of the reactions catalyzed by phosphoribulokinase and NADPH-glyceraldehyde 3-phosphate dehydrogenase by 3 +/- 0.2 and 1.2 +/- 0.3 kJ.mol(-1), respectively. These cofactors have no effect on the independent stable enzymes. Therefore, protein-protein interactions may give rise to new regulatory properties.
Graciet
Emmanuelle
E
Institut Jacques Monod, UMR 7592 CNRS-Universités Paris VI-VII, 2 Place Jussieu, 75 251 Paris Cedex 05, France.
Lebreton
Sandrine
S
Camadro
Jean-Michel
JM
Gontero
Brigitte
B
D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology; D004795:Enzyme Stability; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D009249:NADP / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013816:Thermodynamics
D009249:NADP; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D017853:Phosphotransferases (Alcohol Group Acceptor); C022390:phosphoribulokinase