The purification and properties of isocitrate lyase from Chlorella

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Abstract
Isocitrate lyase (threo-D8-isocitrate glyoxylate-lyase, EC 4.1.3.1) was purified from acetate-adapted cells of Chlorella pyrenoidosa. The final preparation was homogenous by the criteria of sedimentation, diffusion and polyacrylamide-gel electrophoresis. The sedimentation coefficient (S20,w) WAS 9.04 X 10-13 sec. and the diffusion coefficient (D20,w) 4.62 X 10-7 cm.2/sec; from these values the molecular weight of the enzyme was calculated to be 170,000 and its Stokes radius to be 4.63 x 10-7 cm. 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. The turnover number of the enzyme was 5950 moles of glyoxylate formed/min./mole of enzyme at 30[degree]. With threo-DS(+)-isocitrate as substrate, the Km of the enzyme was 0.023 mM.