Effect of Nitric Oxide on the Interaction Between Mitochondrial Malate Dehydrogenase and Citrate Synthase

摘要

cqvip:Mitochondrial malate dehydrogenase(m MDH) and citrate synthase(CS) are sequential enzymes in Krebs cycle. m MDH, CS and the complex between m MDH and CS(m MDH+CS) were treated with nitric oxide solution. The roles of notric oxide(NO) on the secondary structures and the interactions between m MDH and CS were studied using circular diehroism(CD) and Fourier transform surface plasmon resonance(FT-SPR), respectivley. The effects of NO on the activities of mM DH, CS and mM DH+CS were also studied. And the regulations by NO on m MDH and CS were simulated by Py MOL software. The results of SPR confirmed that strong interaction between m MDH and CS existed and NO could significantly regulate the interaction between the two enzymes. NO reduced the mass percents of α-helix and increased that of random in m MDH, CS and m MDH+CS. NO increased the activities of CS and m MDH+CS, and inhibited the activity of m MDH. Graphic simulation indicated that covalent bond was formed between NO and Asn242 in active site of CS. However, there was no direct bond between NO and m MDH. The increase in activity of mM DH+CS complex depended mostly on the interaction between NO and CS. All the results suggested that the regulations by NO on the activity and interaction between m MDH and CS were accord with the changes in m MDH, CS and m MDH+CS caused by NO.