Quantitative LC-QTOF Analysis of Metabolic Pathway

The LC-QTOF analysis of l-histidinol phosphate (Hisol-P), l-histidinol (Hisol) l-histidine (His), imidazole-glycerol phosphate (IGP), adenylosuccinate (AdSucc), 1-(5′-phosphoribosyl)-5-amino-4-imidazolecarboxamide (AICAR), phosphoribosyl-N-formylglycineamide (FGAR), inosine monophosphate (IMP), phosphoribosyl-aminoimidazolesuccinocarboxamide (SAICAR), adenosine monophosphate (AMP), and the pentose 5-phosphate pool (R5P) was carried out as previously described [17 (link)]. Automated data analysis with the “Batch Isotopologue Extraction” feature and natural isotopologue background subtraction was carried out in the MassHunter ProFinder (B.08.00, Agilent Technologies, Santa Clara, CA, USA) software. The relative isotopologue abundances (RIA) of the m + 5 isotopologue for the twelve measured metabolites for every time point was calculated according to: $$\begin{gathered} RI{A}_{m+5}\left[\%\right]=\frac{Intensity m+5}{{{\displaystyle \sum }}_{j=0}^{n}Intensity m+j} \\ n=amount of carbon atoms \end{gathered}$$
Throughout the analysis, the internal standard l-norvaline was monitored to investigate the possible intensity drifts on a global MS level.