Abstract

Tea is one of the most popular beverages consumed throughout the world. It is a source of important secondary metabolites like monoterpenoids, carotenoids and catechins. Monoterpenoids and carotenoids are important constituents of tea aroma. The formation of tea aroma involves synthesis and release of volatile monoterpenoids and carotenoids. On the other hand, catechins are responsible for the beneficial health effects of tea. Detailed in silico analysis of enzymes: Phytoene Synthase (PSY), a key enzyme in the carotenoid biosynthetic pathway and β-primeverosidase (BPR), a diglycosidase responsible for release of bound volatile terpenoids, have been undertaken in this study. Similarly, to study catechin biosynthesis, key enzymes in the flavonoid pathway namely, flavanone-3-hydroxylase (F3H), dihydroflavonol-4-reductase (DFR) and leucoanthocyanidin reductase (LAR), have been identified and studied. The comparative sequence analysis of PSY, F3H, DFR and LAR was carried out to identify the consensus and conserved amino acids using multiple sequence alignment. Phylogenetic trees were created to understand the evolutionary relationship of these enzymes present in different species. The three dimensional model structures were obtained for PSY, BPR, F3H, DFR and LAR by homology modeling to gain insights into the structure function relationships of these enzymes. Multiple templates were used to generate more accurate models of the enzymes. The models were further improved by loop refining and energy minimization. Binding pocket analysis was also done to identify the putative substrate binding sites and understand the enzyme-substrate interactions of each of these enzymes. The computational analysis of these key enzymes, PSY, BPR, F3H, DFR and LAR, provided valuable insights into the mechanism of formation of tea aroma and the synthesis of bioactive secondary metabolites like catechins.

Key words: Camellia sinensis, catechin, modeller, phytoene synthase, β-primeverosidase, flavanone-3-hydroxylase, dihydroflavonol-4-reductase, leucoanthocyanidin reductase.