Catalytic promiscuity of the non-native FPP substrate in the TEAS enzyme: non-negligible flexibility of the carbocation intermediate

Abstract

The TEAS, one of the sesquiterpene cyclases (FPPC), shows enzyme promiscuity that can effectively catalyze both the natural substrate (trans,trans)-FPP and the non-native (cis,trans)-FPP substrate to generate diverse products/byproducts. So far, the catalytic mechanism of the promiscuous substrate is still unclear. In this work, QM(DFT)/MM MD simulations were employed to illuminate the predominant 1,6-closure pathway reaction mechanism for the non-native substrate (cis,trans)-FPP, while the 1,10-closure pathway is the major reaction for the native substrate. It has been revealed that the catalytic promiscuity of TEAS is mostly attributable to the notable conformational dynamics of the branching intermediate bisabolyl cation. The comparative studies to FSTS (another widely studied FPPC) further indicate that the intrinsic intermediate flexibility in TEAS is highly correlated to the plasticity of the enzyme active site pocket contour. Finally, we propose a general picture for controlling the promiscuity and fidelity in FPPC catalysis, including substrate folding, intermediate flexibility and key residues.

Rationally engineering santalene synthase to readjust the component ratio of sandalwood oil

“…3 h and 4f ). These results document that the structural features, especially the cavity space, substantially contribute to configure preorganized substrate folding modes and give rise to various intermediate conformations with different dynamic behavior 25 , 32 .…”

Enzymatic Plasticity Inspired by the Diterpene Cyclase CotB2

“…53 It is also well-known that product scaffolds from plant terpene cyclases are more diverse than that from microorganisms. 53,54 So far, there are more than 2000 diterpene natural products derived from plant family Euphorbiaceae and only about 700 diterpene compounds derived from microorganism, according to our TeroKit database (http://terokit.qmclab.com/). 55 To probe the plasticity of microorganism-derived and Euphorbiaceaederived diterpene cyclases, the active pockets are compared in Figure 6; herein microorganism terpene cyclases are represented by the bacterial diterpene cyclase CotB2 and fungal diterpene cyclase PaFS, while a Ricinus communis casbene synthase (RcCS) 56−58 is employed as a representative example of Euphorbiaceae terpene cyclases.…”

Exploring Chemical and Biological Space of Terpenoids

“…Besides the first dominant scaffold for fungi (Figure ), the rest of 14 dominant scaffolds are not detected in the top 50 list for all terpenoid NPs (Figure ); it indicates that the plant-derived terpenoids represent the most diverse scaffold of all terpenoid NPs. This might be due to the fact that promiscuous terpenoid-related enzymes widely exist in plants, while high fidelity is detected in animals and bacteria. ,− Moreover, the more unique scaffolds in animals and the less unique ones in fungi are consistent with the evolutionary relationship, in which fungi are the nearest to plants and animals are the furthest from plants. Interestingly, the epoxide ring is prevalent in the top 5 high-frequency scaffolds of animal-derived terpenoid NPs; for example, the oxidized γ-lactone-bearing bicyclo[8.4.0] ring (11th/13th/14th in Figure ) exclusively exists in animals.…”