Fig 2: (A) PEPD activity in GG4 and brain, presented as an nmol of PEPD released within 1 min per milligram of protein. (B) Representative zymogram image (Supplementary Materials, Figure S3) of activity of MMP-2 and MMP-9 in the brain and GG4 and results of densitometry analysis for all samples. Results are presented in arbitrary units with the control set as 100. (C) Schematic route of collagen breakdown catalyzed by MMPs and PEPD. Created with BioRender.com (accessed on 10 November 2023).

Fig 3: (A) Representative blot images of Western immunoblot for the enzymes of the proline cycle in GG4, i.e., POX/PRODH, PYCR1, PYCR2, PYCR3, and PEPD, compared to control samples of brain tissue (Supplementary Materials, Figure S2). Results are presented in arbitrary units with the control set as 1. GAPDH was used as a loading control. Densitometry of protein stains is presented under protein bands as intensity ratio versus control. (B) Relative GG4 expression of POX/PRODH, PYCR1, PYCR2, PYCR3, and PEPD compared to control samples of brain tissue. Results are presented in arbitrary units with the control set as 100. Created with BioRender.com (accessed on 10 November 2023).

Fig 4: (A) Transcript levels of POX/PRODH, PYCR1, PYCR2, PYCR3, PEPD, MMP-2, and MMP-9 compared to control samples of brain tissue. The results are presented in arbitrary units with the control set as 1. (B) Comparison of transcript levels of POX/PRODH, PYCR1, PYCR2, PYCR3, PEPD, MMP-2, and MMP-9 genes between TCGA GBM cancer cohort (n = 163) and control brain tissue (n = 207) based on the GTEx samples. Differences are statistically significant at p < 0.05, marked with an asterisk (*). Created with BioRender.com (accessed on 10 November 2023).