When considering ICT oxidative decarboxylation (i.e. forward reaction), heterozygous substitution of R132 in IDH1 with any one of the six amino acids observed in gliomas (i.e. histidine, serine, glycine, cysteine, valine, and leucine) impaired interactions of the enzyme with ICT both sterically and electrostatically. The gene discussed is IDH1; the disease is central nervous system cancer.