The role of specific enzymes in biosynthesis Essay

tannins, stilbenoids, and isoflavonoids. The presence or absence of specific enzymes plays an important role in the biosynthesis of a specific flavonoid in the specific group of plants. Leguminous plant produced special type of secondary metabolites i.e isoflavonoids. The isoflavonoid biosynthesis pathway goes through two branches with majority of same reactions to synthesize key compounds in legumes (Veitch, 2007). Isoflavonoid backbones are synthesized through a series of enzymatic reactions which starts with the deamination of amino acid phenylalanine as a precursor through the shikimate pathway into cinnamate by the enzyme phenylalanine ammonia lyase. Cinnamate is subsequently hydroxylated into pcoumarate and then converted to pcoumaroyl CoA with the help of the enzymes cinnamate 4hydroxylase and 4coumarate CoAligase, respectively (Vadivel et al., 2015).
Narigenin work as transitional compound in the synthesis of genistein in phenylpropanoid pathway to synthesize flavonoids by the action of most common enzymes i.e CHS and CHI (Lozovaya et al. 2007 Moore et al. 2007 Di et al. 2008). The chalcone synthase (CHS) combine with three molecules of malonylCoA to convert it into naringenin chalcone (4,2,4,6tetrahydroxychalcone) (Yu et al. 2003 Li et al. 2011). The isoliquiritigenin and naringenin chalcone synthesized by the coaction of chalcone reductase (CHR) with chalcone synthase (CHS) (Austin and Noel 2003) and synthesis of isoflavonoid compounds begins with the synthesis of central isoflavanone intermediates naringenin and liquiritigenin, respectively. The cytochrome P450 enzyme CYP93C, isoflavone synthase (IFS) initiates the first step of isoflavonoid biosynthetic pathway by transferring the Bring from 2 to the 3position and 2hydroxyisoflavanone formed (Steele et al. 1999 Jung et al. 2000). The 2hydroxyisoflavanone dehydratase (HID) converts the 2hydroxyisoflavanone into daidzein and genistein (Akashi et al. 2005). A series of reactions take place that used daidzein as precursor to produce key phytoalexins, glyceollins, in soybean (Suzuki et al. 2007 Modolo et al. 2007 Lozovaya et al. 2004 Morris et al. 1998 LatundeDada et al. 2001 Lozovaya et al. 2007). Glyceollins are host induced antimicrobial compounds in response to pathogen attack or other stress. As shown in Fig. 1, daidzein undergoes a sequential hydroxylation and reduction process catalyzed by the enzymes isoflavone 2hydroxylase and 2hydroxydaidzein reductase, respectively producing 2hydroxy2,3dihydroxydaidzein. A pterocarpan synthase performs the pterocarpan ring closure and produces 3,9dihydroxypterocarpan, which further gets hydroxylated by a cytochrome P450 monooxygenase, pterocarpan 6ahydroxylase, to yield glycinol [(6aS, 11aS)3,9,6atrihydroxypterocarpan]. Glycinol molecules get subsequently prenylated with the help of isoflavonoidspecific prenyltransferases. This reaction involves the dimethylallylation of glycinol at the C2 or C4 position to yield dimethylallylglycinols, which are further modified by cyclases to produce different glyceollin derivatives. Plant prenyltransferases are involved in various biological processes that pertain to both primary and secondary metabolism, e.g. ubiquinone synthesis (Ohara et al. 2006), shikonin biosynthesis (Yazaki et al. 2002), or vitamin E synthesis (Sadre et al. 2006 Tian et al. 2007 Venkatesh et al. 2006). The known flavonoid or isoflavonoid prenyltransferases include naringenin 8prenyltransferase SfN8DT1 from Sophora flavescens (Sasaki et al.2008) and LaPT1 from Lupinus albus (Shen et al. 2012). Prenyltransferases modify their substrate through a FriedelCraft alkylation which adds