Enzymatic malonylation of natural glycosides provides a promising alternative method for drug-like malonylated glycosides supply.However,the catalytic potential and structural basis of plant malonyltransferase are far from being fully elucidated.This work identified a new malonyltransferase CtMaT1 from Cistanche tubulosa.It displayed unprecedented mono-and/or di-malonylation activity toward diverse glucosides with different aglycons.A“one-pot”system by CtMaT1 and a malonyl-CoA synthetase was established to biosynthesize nine new malonylated glucosides.Structural investigations revealed that CtMaT1 possesses an adequately spacious acyl-acceptor pocket capable of accommodating diverse glucosides.Additionally,it recognizes malonyl-CoA through strong electrotactic and hydrogen interactions.QM/MM calculation revealed the H167-mediated SN2 reaction mechanism of CtMaT1,while dynamic simulations detected the formation of stable hydrogen bonds between the glucose-6-OH group and H167,resulting in its high malonylation regiospecificity.Calculated energy profiles of two isomeric glycosides highlighted lower reaction energy barriers towards glucoside substrates,emphasizing CtMaT1's preference for glucosides.Furthermore,a mutant CtMaT1H36A with notably increased di-malonylation activity was obtained.The underlying molecular mechanism was illuminated through MM/GBSA binding free energy calculation.This study significantly advances the understanding of plant acyltransferases from both functional and protein structural perspectives,while also providing a versatile tool for enzymatic malonylation applications in pharmacology.
Fungal bifunctional terpene synthases(BFTSs)catalyze the formation of numerous di-/sester-/tri-terpenes skeletons.However,the mechanism in controlling the cyclization pattern of terpene scaffolds is rarely deciphered for further application of tuning the catalytic promiscuity of terpene synthases for expanding the chemical space.In this study,we expanded the catalytic promiscuity of Fusarium oxysporum fusoxypene synthase(FoFS)by a single mutation at L89,leading to the production of three new sesterterpenes.Further computational analysis revealed that the reconstitution of the hydrogen-bond(H-bond)network of second-shell residues around the active site of FoFS influences the orientation of the aromatic residue W69 within the first-shell catalytic pocket.Thus,the dynamic orientation of W69 alters the carbocation transport,leading to the production of diverse ring system skeletons.These findings enhance our knowledge on understanding the molecular mechanisms,which could be applied on protein engineering terpene synthases on regulating the terpene skeletons.
In a recent article in Nature,Muthusami et al.1 highlight the promiscuity of serine palmitoyltransferase(SPT)for non-essential amino acids under low serine conditions,illustrating a previously unappreciated mechanism for inhibition of tumour growth—increased levels of deoxysphingolipids.
A new method for the synthesis of 1,4-dihydropyridine(1,4-DHP)calcium channel antagonists felodipme, nitrendipine and their derivatives via papain-catalyzed three-component reactions of aldehyde,methyl acetoacetate and ethyl 3-aminocrotonate was developed.Operational simplicity,mild reaction conditions and eco-friendliness are the key features of this protocol.
