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Plant Physiology 65:949-955 (1980)
© 1980 American Society of Plant Biologists

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Articles

Purification and Characterization of the Crown Gall-specific Enzyme, Octopine Synthase 1

Ethan Hack and John D. Kemp

Plant Disease Resistance Research Unit, Agricultural Research, United States Department of Agriculture, University of Wisconsin, Madison, Wisconsin 53706, Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53706

A single enzyme catalyzes the synthesis of all four N2-(1-carboxyethyl)-amino acid derivatives found in a crown gall tumor tissue induced by Agrobacterium tumefaciens (E. F. Sm. and Town.) Conn strain B6 on sunflower (Helianthus annuus L.). This enzyme, octopine synthase, has been purified by ammonium sulfate fractionation and chromatography on diethylaminoethylcellulose, blue agarose, and hydroxylapatite. The purified enzyme has all the N2-(1-carboxyethyl)-amino acid synthesizing activities found in crude preparations, and the relative activities with six amino acids remain nearly constant during purification. Although the maximum velocities (V) and Michaelis constants (Km) differ, the ratio V/Km is the same for all amino acid substrates. Thus an equimolar mixture of amino acids will give rise to an equimolar mixture of products. The kinetic properties of the enzyme are consistent with a partially ordered mechanism with arginine (NADPH, then arginine or pyruvate). Octopine synthase is a monomeric enzyme with a molecular weight of 39,000 by gel filtration and 38,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

1 Research cooperative with the College of Agricultural and Life Sciences, University of Wisconsin, Madison, and the United States Department of Agriculture. E. H. was the recipient of Predoctoral Training Grant 5T32 GM07215 from United States Public Health Service.






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Copyright © 1980 by the American Society of Plant Biologists