AbstractIsocitrate lyase purified to homogeneity from Saccharomyces cerevisiae was composed of four identical subunits with a molecular mass 75 K Da. The enzyme was most active at pH 7.0 in the presence of 5 mM‐Mg2+. The Km value for threo‐Ds‐isocitrate was 1.4 mM. Isocitrate lyase was shown to be thermostable at 50°C for 60 min at a high salt concentration, but rapidly lost activity at −20°C or by dialysis.