Dataset Information

Predicting Flavonoid UGT Regioselectivity.

ABSTRACT: MACHINE LEARNING WAS APPLIED TO A CHALLENGING AND BIOLOGICALLY SIGNIFICANT PROTEIN CLASSIFICATION PROBLEM: the prediction of avonoid UGT acceptor regioselectivity from primary sequence. Novel indices characterizing graphical models of residues were proposed and found to be widely distributed among existing amino acid indices and to cluster residues appropriately. UGT subsequences biochemically linked to regioselectivity were modeled as sets of index sequences. Several learning techniques incorporating these UGT models were compared with classifications based on standard sequence alignment scores. These techniques included an application of time series distance functions to protein classification. Time series distances defined on the index sequences were used in nearest neighbor and support vector machine classifiers. Additionally, Bayesian neural network classifiers were applied to the index sequences. The experiments identified improvements over the nearest neighbor and support vector machine classifications relying on standard alignment similarity scores, as well as strong correlations between specific subsequences and regioselectivities.

SUBMITTER: Jackson R

PROVIDER: S-EPMC3130495 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Predicting Flavonoid UGT Regioselectivity.

Jackson Rhydon R Knisley Debra D McIntosh Cecilia C Pfeiffer Phillip P

Advances in bioinformatics 20110630

MACHINE LEARNING WAS APPLIED TO A CHALLENGING AND BIOLOGICALLY SIGNIFICANT PROTEIN CLASSIFICATION PROBLEM: the prediction of avonoid UGT acceptor regioselectivity from primary sequence. Novel indices characterizing graphical models of residues were proposed and found to be widely distributed among existing amino acid indices and to cluster residues appropriately. UGT subsequences biochemically linked to regioselectivity were modeled as sets of index sequences. Several learning techniques incorpo ...[more]

PMID: 21747849

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Project description:BackgroundFlavonoids are secondary metabolites that play significant roles in plant cells. In particular, polymethoxy flavonoids (PMFs), including nobiletin, have been reported to exhibit various health-supporting properties such as anticancer, anti-inflammatory, and anti-pathogenic properties. However, it is difficult to utilize PMFs for medicinal and dietary use because plant cells contain small amounts of these compounds. Biosynthesis of PMFs in plant cells is carried out by the methylation of hydroxyl groups of flavonoids by O-methyltransferases (FOMT), and many kinds of FOMTs with different levels of substrate specificity and regioselectivity are cooperatively involved in this biosynthesis.ResultsIn this study, we isolated five genes encoding FOMT (CdFOMT1, 3, 4, 5, and 6) from Citrus depressa, which is known to accumulate nobiletin in the peels of its fruits. The genes encoded Mg(2+)-independent O-methyltransferases and showed high amino acid sequence similarity (60-95 %) with higher plant flavonoid O-methyltransferases. One of these genes is CdFOMT5, which was successfully expressed as a soluble homodimer enzyme in Escherichia coli. The molecular mass of the recombinant CdFOMT5 subunit was 42.0 kDa including a 6× histidine tag. The enzyme exhibited O-methyltransferase activity for quercetin, naringenin, (-)-epicatechin, and equol using S-adenosyl-L-methionine (SAM) as a methyl donor, and its optimal pH and temperature were pH 7.0 and 45 °C, respectively. The recombinant CdFOMT5 demonstrated methylation activity for the 3-, 5-, 6-, and 7-hydroxyl groups of flavones, and 3,3',5,7-tetra-O-methylated quercetin was synthesized from quercetin as a final product of the whole cell reaction system. Thus, CdFOMT5 is a O-methyltransferase possessing a broad range of substrate specificity and regioselectivity for flavonoids.ConclusionsFive FOMT genes were isolated from C. depressa, and their nucleotide sequences were determined. CdFOMT5 was successfully expressed in E. coli cells, and the enzymatic properties of the recombinant protein were characterized. Recombinant CdFOMT5 indicated O-methyltransferase activity for many flavonoids and a broad regioselectivity for quercetin as a substrate. Whole-cell biocatalysis using CdFOMT5 expressed in E. coli cells was performed using quercetin as a substrate, and 3,3',5,7-tetramethylated quercetin was obtained as the final product.

Dataset Information

Predicting Flavonoid UGT Regioselectivity.

Publications

Predicting Flavonoid UGT Regioselectivity.

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