AVOCADO POLYPHENOLOXIDASE: PURIFICATION, AND FRACTIONATION ON SEPHADEX THIN LAYERS

Abstract

SUMMARY Polyphenoloxidase (PPO) was purified 28‐fold by ammonium sulfate precipitation, dialysis and gel filtration. Enzyme constants were determined with a variety of substrates. Thinlayer gel filtration resolved the crude PPO in to 5 fractions with molecular weights estima ted at 14‐, 28‐, 56‐, 112‐ and over 400‐thousand by comparison with standard proteins. Subsequent electrophoresis at 90° to the direction of gel filtration resolved the 28 × 10 3 MW fraction into 4 to 6 components. One of these was by. far the most active of all the isoenzymes toward all the substrate sprays tested. It is probably the activity of this isoenzyme which is reflected in kinetic data, even those obtained with relatively crude avocado PPO preparations.