Biomaterial Database

Purification, cloning, and heterologous expression of a catalytically efficient flavonol 3-O-galactosyltransferase expressed in the male gametophyte of Petunia hybrida. 1999

K D Miller, and V Guyon, and J N Evans, and W A Shuttleworth, and L P Taylor

Program in Plant Physiology, Washington State University, Pullman, Washington 99164-6340, USA.

Flavonols are plant-specific molecules that are required for pollen germination in maize and petunia. They exist in planta as both the aglycone and glycosyl conjugates. We identified a flavonol 3-O-galactosyltransferase (F3GalTase) that is expressed exclusively in the male gametophyte and controls the formation of a pollen-specific class of glycosylated flavonols. Thus an essential step to understanding flavonol-induced germination is the characterization of F3GalTase. Amino acid sequences of three peptide fragments of F3GalTase purified from petunia pollen were used to isolate a full-length cDNA clone. RNA gel blot analysis and enzyme assays confirmed that F3GalTase expression is restricted to pollen. Heterologous expression of the F3GalTase cDNA in Escherichia coli yielded active recombinant enzyme (rF3GalTase) which had the identical substrate specificity as the native enzyme. Unlike the relatively nonspecific substrate usage of flavonoid glycosyltransferases from sporophytic tissues, F3GalTase uses only UDP-galactose and flavonols to catalyze the formation of flavonol 3-O-galactosides. Kinetic analysis showed that the k(cat)/K(m) values of rF3GalTase, using kaempferol and quercetin as substrates, approaches that of a catalytically perfect enzyme. rF3GalTase catalyzes the reverse reaction, generation of flavonols from UDP and flavonol 3-O-galactosides, almost as efficiently as the forward reaction. The biochemical characteristics of F3GalTase are discussed in the context of a role in flavonol-induced pollen germination.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010944	Plants	Multicellular, eukaryotic life forms of kingdom Plantae. Plants acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations. It is a non-taxonomical term most often referring to LAND PLANTS. In broad sense it includes RHODOPHYTA and GLAUCOPHYTA along with VIRIDIPLANTAE.	Plant
D011058	Pollen	The fertilizing element of plants that contains the male GAMETOPHYTES.	Male Gametes, Plant,Male Gametophytes,Microspores, Plant,Plant Microspores,Pollen Grains,Gamete, Plant Male,Gametes, Plant Male,Gametophyte, Male,Gametophytes, Male,Grain, Pollen,Grains, Pollen,Male Gamete, Plant,Male Gametophyte,Microspore, Plant,Plant Male Gamete,Plant Male Gametes,Plant Microspore,Pollen Grain
D011993	Recombinant Fusion Proteins	Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes.	Fusion Proteins, Recombinant,Recombinant Chimeric Protein,Recombinant Fusion Protein,Recombinant Hybrid Protein,Chimeric Proteins, Recombinant,Hybrid Proteins, Recombinant,Recombinant Chimeric Proteins,Recombinant Hybrid Proteins,Chimeric Protein, Recombinant,Fusion Protein, Recombinant,Hybrid Protein, Recombinant,Protein, Recombinant Chimeric,Protein, Recombinant Fusion,Protein, Recombinant Hybrid,Proteins, Recombinant Chimeric,Proteins, Recombinant Fusion,Proteins, Recombinant Hybrid
D002384	Catalysis	The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.	Catalyses
D003001	Cloning, Molecular	The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.	Molecular Cloning
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D005700	Galactosyltransferases	Enzymes that catalyze the transfer of galactose from a nucleoside diphosphate galactose to an acceptor molecule which is frequently another carbohydrate. EC 2.4.1.-.	Galactosyltransferase
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations