The purification and properties of isocitrate lyase from Chlorella
1. Isocitrate lyase (threo-ds-isocitrate glyoxylate-lyase, EC 4.1.3.1) has been purified from acetate-adapted cells of Chlorella pyrenoidosa. 2. The final preparation was homogeneous by the criteria of sedimentation, diffusion and polyacrylamide-gel electrophoresis. 3. The sedimentation coefficient (S20,w) was 9·04×10−13sec. and the diffusion coefficient (D20,w) 4·62×10−7cm.2/sec.; from these values the molecular weight of the enzyme was calculated to be 170000 and its Stokes radius to be 4·63×10−7cm. 4. The elution of the enzyme from Sephadex G-100 was studied and estimates of molecular weight and Stokes radius were obtained from the elution data. 5. The turnover number of the enzyme was 5950moles of glyoxylate formed/min./mole of enzyme at 30°. 6. With threo-ds(+)-isocitrate as substrate, the Km of the enzyme was 0·023mm.