Study summary · research use only
Characterization of AICAR transformylase/IMP cyclohydrolase (ATIC) bifunctional enzyme from Candidatus Liberibacer asiaticus
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This study characterized the bifunctional enzyme AICAR transformylase/IMP cyclohydrolase (ATIC) from the bacterium Candidatus Liberibacer asiaticus (CLasATIC) using in vitro biochemical assays and CHO cell-based bioassays. The abstract reports AICAR transformylase activity with a Km of 146.6 μM and Vmax of 0.95 μmol/min/mg for the substrate 10-f-THF, and a Km of 34.81 μM and Vmax of 0.56 μmol/min/mg for AICAR, along with IMP cyclohydrolase activity (Km 1.81 μM, Vmax 2.87 μmol/min/mg). Virtual screening and MD simulations identified HNBSA, diosbulbin A, and lepidine D as candidate inhibitors, with ITC studies reporting binding affinities (Kd) of 12.3 μM and 34.2 μM for HNBSA and diosbulbin A respectively, versus 83.4 μM for AICAR. CLasATIC also showed cell proliferative, wound-healing, and reactive-oxygen-species-scavenging activity in the CHO cell assays.
Abstract
The bifunctional enzyme, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase/inosine monophosphate (IMP) cyclohydrolase (ATIC) is involved in catalyzing penultimate and final steps of purine de novo biosynthetic pathway crucial for the survival of organisms. The present study reports the characterization of ATIC from Candidatus Liberibacer asiaticus (CLasATIC) along with the identification of potential inhibitor molecules and evaluation of cell proliferative activity. CLasATIC showed both the AICAR Transformylase (AICAR TFase) activity for substrates, 10-f-THF (Km, 146.6 μM and Vmax, 0.95 μmol/min/mg) and AICAR (Km, 34.81 μM and Vmax, 0.56 μmol/min/mg) and IMP cyclohydrolase (IMPCHase) activitiy (Km, 1.81 μM and Vmax, 2.87 μmol/min/mg). The optimum pH and temperature were also identified for the enzyme activity. In-silico study has been conducted to identify potential inhibitor molecules through virtual screening and MD simulations. Out of many compounds, HNBSA, diosbulbin A and lepidine D emerged as lead compounds, exhibiting higher binding energy and stability for CLasATIC than AICAR. ITC study reports higher binding affinities for HNBSA and diosbulbin A (Kd, 12.3 μM and 34.2 μM, respectively) compared to AICAR (Kd, 83.4 μM). Likewise, DSC studies showed enhanced thermal stability for CLasATIC in the presence of inhibitors. CD and Fluorescence studies revealed significant conformational changes in CLasATIC upon binding of the inhibitors. CLasATIC demonstrated potent cell proliferative, wound healing and ROS scavenging properties evaluated by cell-based bioassays using CHO cells. This study highlights CLasATIC as a promising drug target with potential inhibitors for managing CLas and its unique cell protective, wound-healing properties for future biotechnological applications.
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