Two Different Isocitrate Dehydrogenases from IPseudomonas aeruginosa/I: Enzymology and Coenzyme-Evolutionary Implications

• Published in: International journal of molecular sciences 2023-10, Vol.24 (19)
• Main Authors: Chen, Xuefei, Wei, Wei, Xiong, Wei, Wu, Shen, Wu, Quanchao, Wang, Peng, Zhu, Guoping
• Format: Article
• Language: English
• Subjects: Amino acids; Cystic fibrosis; Disease susceptibility; Drug resistance in microorganisms; Oxidoreductases
• ISSN: 1422-0067
• DOI: 10.3390/ijms241914985

Pseudomonas aeruginosa PAO1, as an experimental model for Gram-negative bacteria, harbors two NADP[sup.+]-dependent isocitrate dehydrogenases (NADP-IDHs) that were evolved from its ancient counterpart NAD-IDHs. For a better understanding of PaIDH1 and PaIDH2, we cloned the genes, overexpressed them in Escherichia coli and purified them to homogeneity. PaIDH1 displayed higher affinity to NADP[sup.+] and isocitrate, with lower Km values when compared to PaIDH2. Moreover, PaIDH1 possessed higher temperature tolerance (50 °C) and wider pH range tolerance (7.2–8.5) and could be phosphorylated. After treatment with the bifunctional PaIDH kinase/phosphatase (PaIDH K/P), PaIDH1 lost 80% of its enzymatic activity in one hour due to the phosphorylation of Ser115. Small-molecule compounds like glyoxylic acid and oxaloacetate can effectively inhibit the activity of PaIDHs. The mutant PaIDH1-D346I347A353K393 exhibited enhanced affinity for NAD[sup.+] while it lost activity towards NADP[sup.+], and the Km value (7770.67 μM) of the mutant PaIDH2-L589 I600 for NADP[sup.+] was higher than that observed for NAD[sup.+] (5824.33 μM), indicating a shift in coenzyme specificity from NADP[sup.+] to NAD[sup.+] for both PaIDHs. The experiments demonstrated that the mutation did not alter the oligomeric state of either protein. This study provides a foundation for the elucidation of the evolution and function of two NADP-IDHs in the pathogenic bacterium P. aeruginosa.