Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/201417
Type: Artigo de periódico
Title: Molecular And Biochemical Characterization Of Caffeine Synthase And Purine Alkaloid Concentration In Guarana Fruit.
Author: Schimpl, Flávia Camila
Kiyota, Eduardo
Mayer, Juliana Lischka Sampaio
Gonçalves, José Francisco de Carvalho
da Silva, José Ferreira
Mazzafera, Paulo
Abstract: Guarana seeds have the highest caffeine concentration among plants accumulating purine alkaloids, but in contrast with coffee and tea, practically nothing is known about caffeine metabolism in this Amazonian plant. In this study, the levels of purine alkaloids in tissues of five guarana cultivars were determined. Theobromine was the main alkaloid that accumulated in leaves, stems, inflorescences and pericarps of fruit, while caffeine accumulated in the seeds and reached levels from 3.3% to 5.8%. In all tissues analysed, the alkaloid concentration, whether theobromine or caffeine, was higher in young/immature tissues, then decreasing with plant development/maturation. Caffeine synthase activity was highest in seeds of immature fruit. A nucleotide sequence (PcCS) was assembled with sequences retrieved from the EST database REALGENE using sequences of caffeine synthase from coffee and tea, whose expression was also highest in seeds from immature fruit. The PcCS has 1083bp and the protein sequence has greater similarity and identity with the caffeine synthase from cocoa (BTS1) and tea (TCS1). A recombinant PcCS allowed functional characterization of the enzyme as a bifunctional CS, able to catalyse the methylation of 7-methylxanthine to theobromine (3,7-dimethylxanthine), and theobromine to caffeine (1,3,7-trimethylxanthine), respectively. Among several substrates tested, PcCS showed higher affinity for theobromine, differing from all other caffeine synthases described so far, which have higher affinity for paraxanthine. When compared to previous knowledge on the protein structure of coffee caffeine synthase, the unique substrate affinity of PcCS is probably explained by the amino acid residues found in the active site of the predicted protein.
Subject: Alkaloids
Amino Acid Sequence
Base Sequence
Caffeine
Fruit
Methylation
Methyltransferases
Molecular Structure
Paullinia
Plant Leaves
Purines
Seeds
Theobromine
Theophylline
Xanthines
Amazon
Caffeine
Paullinia Cupana Var. Sorbilis
Recombinant Protein
Sapindaceae
Seed
Theobromine
Venezuelan Guarana
Rights: fechado
Identifier DOI: 10.1016/j.phytochem.2014.04.018
Address: http://www.ncbi.nlm.nih.gov/pubmed/24856135
Date Issue: 2014
Appears in Collections:Unicamp - Artigos e Outros Documentos

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