Publications

• Functional expression of an Arabidopsis cDNA clone encoding a flavonol 3'-O-methyltransferase and characterization of the gene product.

  Muzac I., Wang J., Anzellotti D., Zhang H., Ibrahim R.K.

  We report that the cDNA clone (Accession No. U70424), previously isolated from Arabidopsis thaliana as encoding a caffeic acid/5-hydroxyferulic acid O-methyltransferase (OMT) (1), has now been overexpressed in Escherichia coli BL21 and its recombinant protein identified as a novel flavonol 3'-OMT. ... >> More

  We report that the cDNA clone (Accession No. U70424), previously isolated from Arabidopsis thaliana as encoding a caffeic acid/5-hydroxyferulic acid O-methyltransferase (OMT) (1), has now been overexpressed in Escherichia coli BL21 and its recombinant protein identified as a novel flavonol 3'-OMT. It is, therefore, renamed AtOMT1. This cDNA clone has previously been identified on the basis of its 88% amino acid sequence similarity and 80% identity to the aspen bispecific lignin OMT (2), the type member of the group involved in lignin biosynthesis. Our data indicate that this novel OMT uses the flavonol quercetin as the preferred substrate, but neither of the hydroxycinnamic acids, caffeic or 5-hydroxyferulic, to any significant extent. This indicates that the high sequence similarity/identity of AtOMT1 to that of the aspen lignin OMT (2) is not sufficient to assign the function of this gene product. << Less

  Arch. Biochem. Biophys. 375:385-388(2000) [PubMed] [EuropePMC]

• O-Methylation of flavonoid substrates by a partially purified enzyme from soybean cell suspension cultures.

  Poulton J.E., Hahlbrock K., Grisebach H.

  Arch Biochem Biophys 180:543-549(1977) [PubMed] [EuropePMC]

• In vitro characterization of enzymes involved in the synthesis of nonproteinogenic residue (2S,3S)-beta-methylphenylalanine in glycopeptide antibiotic mannopeptimycin.

  Huang Y.T., Lyu S.Y., Chuang P.H., Hsu N.S., Li Y.S., Chan H.C., Huang C.J., Liu Y.C., Wu C.J., Yang W.B., Li T.L.

  Mannopeptimycin, a potent drug lead, has superior activity against difficult-to-treat multidrug-resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). (2S,3S)-beta-Methylphenylalanine is a residue in the cyclic hexapeptide core of mannopeptimycin, but the syn ... >> More

  Mannopeptimycin, a potent drug lead, has superior activity against difficult-to-treat multidrug-resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). (2S,3S)-beta-Methylphenylalanine is a residue in the cyclic hexapeptide core of mannopeptimycin, but the synthesis of this residue is far from clear. We report here on the reaction order and the stereochemical course of reaction in the formation of (2S,3S)-beta-methylphenylalanine. The reaction is executed by the enzymes MppJ and TyrB, an S-adenosyl methionine (SAM)-dependent methyltransferase and an (S)-aromatic-amino-acid aminotransferase, respectively. Phenylpyruvic acid is methylated by MppJ at its benzylic position at the expense of one equivalent of SAM. The resulting beta-methyl phenylpyruvic acid is then converted to (2S,3S)-beta-methylphenylalanine by TyrB. MppJ was further determined to be regioselective and stereoselective in its catalysis of the formation of (3S)-beta-methylphenylpyruvic acid. The binding constant (K(D)) of MppJ versus SAM is 26 microM. The kinetic constants with respect to k(cat Ppy) and K(M Ppy), and k(cat SAM) and K(M SAM) are 0.8 s(-1) and 2.5 mM, and 8.15 s(-1) and 0.014 mM, respectively. These results suggest SAM has higher binding affinity for MppJ than Ppy, and the C--C bond formation in betamPpy might be the rate-limiting step, as opposed to the C--S bond breakage in SAM. << Less

  ChemBioChem 10:2480-2487(2009) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.