This is the external Supplementary Information for our publication "pH-Independent Heat Capacity Changes during Phosphorolysis Catalyzed by the Pyrimidine Nucleoside Phosphorylase from Geobacillus thermoglucosidasius". The .pdf file contains the Supplementary Information: author contributions, experimental procedures and supplementary items. The .zip file contains the raw data and metadata for all items (supplementary and main text) and the calculations. Metadata files were curated by Felix Kaspar and calculation files were created by Darian Wolff. The Python code used for spectral unmixing is available on this platform (10.5281/zenodo.3243376) and has been described in our previous publications (10.3390/mps2030060, 10.5281/zenodo.3333469, 10.1002/cbic.202000204, 10.5281/zenodo.3723806). Further applications of this method can be found in our recent articles in Adv. Synth. Catal. (10.1002/adsc.201901230) and its supporting material (10.5281/zenodo.3568858) and in ChemBioChem (10.1002/cbic.202000679) and its supporting material on this platform (10.5281/zenodo.4284188).