PLANT PHYSIOLOGY , Vol 113, Issue 1 119-126, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Immunopurification and Characterization of a 40-kD 1-Aminocyclopropane-1-Carboxylic Acid N-Malonyltransferase from Mung Bean Seedling Hypocotyls
WSH. Chick and P. C. Leung
Department of Zoology, The University of Hong Kong, Pokfulam Road, Hong Kong
1-Aminocylopropane-1-carboxylic acid (ACC) N-malonyltransferase catalyzes
the transfer of the malonyl group from malonyl coenzyme A to ACC to form
malonyl ACC. Using partially purified ACC N-malonyltransferase from the
hypocotyls of mung bean (Vigna radiata) seedlings, we produced two mouse
monoclonal antibodies (1H5 and 2G3) to this enzyme. These antibodies bind
to sites other than the active site of the enzyme because monoclonal
antibody-bound ACC N-malonyltransferase still exhibits full catalytic
activity. A monoclonal antibody column was constructed using 1H5 and
protein G Sepharose. The ACC N-malonyltransferase purified from this
monoclonal antibody column has a molecular mass of 40 kD, which is
different from that reported previously. The enzyme has a higher
electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gel
electrophoresis in the absence of the reducing agent dithiothreitol. The
optimum temperature of this 40-kD ACC N-malonyltransferase is 45[deg]C and
the apparent Kms for ACC and malonyl coenzyme A are 66.7 and 40 [mu]M,
respectively.