  4.2.3.229 | evolution |
plants have extensively diversified their arsenal of labdane-related diterpenoids (LRDs), in part via gene duplication and neo-functionalization of the ancestral ent-kaurene synthase (KS) required for gibberellin metabolism. Ricinus communis contains 4 RcKSL isozymes, molecular phylogenetic analysis indicates that RcKS(L)1 is significantly more closely related to dicotyl ent-kaurene synthases (KSs), while the other three, RcKSL2-4, cluster separately. RcKSL2-4 are in close proximity to each other, within a region of 65 kb, with RcKSL2 and 4 occurring as a tandem gene pair. RcKS(L)1 is the only isozyme to react with ent-CPP producing small amounts of ent-kaurene, and is referred to as RcKS1. Both RcKSL2 and RcKSL3 also are selectively reacting with ent-CPP with RcKSL2 producing primarily ent-trachylobane (70%) as well as smaller amounts of ent-kaurene (30%), and RcKSL3 producing ent-sandaracopimaradiene (94%) (EC 4.2.3.29) along with small amounts of ent-labdatriene (3%) and ent-pimaradiene (3%). RcKSL4 seems to be inactive, with no products evident from any substrate, but upon synthesis of a codon-optimized gene for the corrected aa sequence and functional analysis, RcKSL4 selectively reacts with ent-CPP and produces largely ent-beyerene (95%) along with very small amounts of ent-atiserene (4%) and ent-kaurene (1%). The enzymes belong to the terpene synthase family |
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