values and D -2-hydroxyglutarate levels of IDH1 mutation types. KM values of IDH1 mutation types for α-ketoglutarate (A) and isocitrate (B). The KM value for α-ketoglutarate of IDH1 wt and the KM values for isocitrate of all IDH1R132 mutations could not be determined. Therefore KM values of R132 mutations are not shown. All KM values are significantly different from each other with a p-value of ≤0.01, if not otherwise stated (* = p ≤ 0.05 or n.s. = not significant). All measurements were done in triplicate from different protein purifications. D-2-hydroxyglutarate levels in HEK293T cells ectopically expressing different IDH1 mutations and wild type IDH1 (C). Levels are measured in cells from one confluent dish of 6-well Plate 72 h after seeding. All D-2-hydroxyglutarate levels of the mutant IDH1 expressing cells are significantly higher (p ≤ 0.01) than both controls (wt and GFP). The levels of all other R132 mutants are significantly higher than the one of R132H (p-value: * = p ≤ 0.05 and ** = p ≤ 0.01). Only the level of R100Q is significant lower than the level of R132H (p-value: ** = p ≤ 0.01).