J. Biol. Chem., Vol. 268, Issue 34, 25389-25394, 12, 1993
Amino acid N-malonyltransferases from mung beans. Action on 1- aminocyclopropane-1-carboxylic acid and D-phenylalanine
L Guo, AT Phillips and RN Arteca
Department of Horticulture, Pennsylvania State University, University Park 16802.
1-Aminocyclopropane-1-carboxylate (ACC) N-malonyltransferase from etiolated
mung bean hypocotyls was examined for its relationship to D- phenylalanine
N-malonyltransferase and other enzymes which transfer malonyl groups from
malonyl-CoA to D-amino acids. Throughout a 3600- fold purification the
ratio of D-phenylalanine N-malonyltransferase activity to ACC
N-malonyltransferase activity was unchanged. Antibodies raised against
purified ACC N-malonyltransferase 55-kDa protein were also able to
precipitate all D-phenylalanine-directed activity from partially purified
mung bean extracts. The irreversible inhibitors phenylglyoxal and
tetranitromethane reduced malonyltransferase activity towards
D-phenylalanine to the same extent as that for ACC. In addition, several
other D-amino acids, particularly D-tryptophan and D- tyrosine, were able
to inhibit action towards both ACC and D- phenylalanine. These lines of
evidence suggest that a single enzyme is capable of promoting malonylation
of both ACC and D-phenylalanine. Km values for D-phenylalanine and
malonyl-CoA were found to be 48 and 43 microM, respectively; these values
are 10-fold lower than the corresponding values when ACC was substrate.
Coenzyme A was a noncompetitive (mixed type) product inhibitor towards
malonyl-CoA at both unsaturated and saturated ACC concentrations. The
enzyme was also inhibited uncompetitively at high concentrations of
malonyl-CoA. We propose that the enzyme follows an Ordered Bi-Bi reaction
pathway, with the amino acid substrate being bound initially.
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