Crystalline Lipoxidase.

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Abstract
In a series of large-scale expts., crystalline enzyme with properties indicating it being a lipoxidase was prepared from soy bean meal; homogeneous according to sedimentation and diffusion patterns. The enzyme was a colorless protein containing no Fe or detectable prosthetic group; molecular wt. 102,000, isoelectric point, pH 5.4. The activity as measured by the spectro-scopical method of Theorell, Angstrom and Akesson (Pharm. Helv. Acta 21: 318. 1946) was of the magnitude of 330 moles of linoleic acid oxidized/mole enzyme/sec; under the conditions of assay used. Starting with a suspension of 15 kg. soy flour in 100 1. of [image]/10 acetate buffer at pH 4.5, large amts. of inactive material were removed, through centrifugation adjusting the pH of the soln. to 6.7 with ammonia and adding 5 vol. 20% BaAc2 soln., 2 vol. 20% basic lead acetate soln. and 10 vol. of acetone/100 vol. of the soln. After removing the inactive precipitate, repeated fractionation with ammonium sulphate (35 up to 50% saturation) finally yielded about 400 mg. of crystalline enzyme free from amorphous material. The absorption spectrum indicated a comparatively large amt. of tyrosin or trypto- phane in the molecule. No heavy metal or any activator was found to increase the activity of the enzyme, in spite of its accomplishing the same reactions towards linoleic acid as heavy metal ions, which "puts lipoxidase into a unique position among the oxidation enzymes known so far.".

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