Heteromeric and Homomeric Geranyl Diphosphate Synthases from Catharanthus roseus and Their Role in Monoterpene Indole Alkaloid Biosynthesis

Catharanthus roseus is the sole source of two most important monoterpene indole alkaloid （MIA） anti- cancer agents： vinblastine and vincristine. MIAs possess a terpene and an indole moiety derived from terpenoid and shikimate pathways, respectively. Geranyl diphosphate （GPP）, the entry point to the formation of terpene moiety, is a product of the condensation of isopentenyl diphosphate （IPP） and dimethylallyl diphosphate （DMAPP） by GPP synthase （GPPS）. Here, we report three genes encoding proteins with sequence similarity to large subunit （CrGPPS.LSU） and small subunit （CrGPPS.SSU） of heteromeric GPPSs, and a homomeric GPPSs. CrGPPS.LSU is a bifunctional enzyme producing both GPP and geranyl geranyl diphosphate （GGPP）, CrGPPS.SSU is inactive, whereas CrGPPS is a homomeric enzyme forming GPP. Co-expression of both subunits in Escherichia coil resulted in heteromeric enzyme with enhanced activity producing only GPR While CrGPPS.LSU and CrGPPS showed higher expression in older and younger leaves, respectively, CrGPPS.SSU showed an increasing trend and decreased gradually. Methyl jasmonate （MelA） treatment of leaves sig- nificantly induced the expression of only CrGPPS.SSU. GFP localization indicated that CrGPPS.SSU is plastidial whereas CrGPPS is mitochondrial. Transient overexpression of AmGPPS.SSU in C. roseus leaves resulted in increased vindoline, immediate monomeric precursor of vinblastine and vincristine. Although C. roseus has both heteromeric and homomeric GPPS enzymes, our results implicate the involvement of only heteromeric GPPS with CrGPPS.SSU regulating the GPP flux for MIA biosynthesis.

Bioproduction of monoterpene indole alkaloids in a single cell factory

The de novo biosynthesis of vindoline and catharanthine,the direct precursors used for industrial production of the anti-cancer drug vinblastine,has been achieved in the yeast cell factory.To date,this is the longest natural product biosynthesis pathway that has been successfully transferred from plants to microorganisms,indicating the possibility of producing more than 3,000 other monoterpene indole alkaloids in yeast by synthetic genome engineering.

Three New Indole Alkaloids from Tabernaemontana divaricata

Three new monoterpene indole alkaloids,3a-hydroxymethyl-ibogamine(1),3a-acetatemethoxyl-ibogamine(2),16a-hy-droxyl-ibogamine(3)together with six known alkaloids were isolated from the branches and leaves of Tabernaemontana divaricata(Apocynaceae).The structures of these alkaloids were determined by spectroscopic analyses.All isolated compounds showed no significant cytotoxicity against SGC-7901 gastric cancer,HeLa,and A-549 lung cancer cell lines(IC50>20μM).

Uncarialines A-E,new alkaloids from Uncaria rhynchophylla and their anticoagulant activity

Uncarialines A-E(1-5),five undescribed monoterpene indole alkaloids,together with five known analogues were obtained from the stems of Uncaria rhynchophylla.Alkaloids 1-3 were unique 3,4-seco-tricyclic alkaloids with a 6/5/10 ring system,while 4 and 5 possessed a rare rearranged scaffold originated from corynantheine-type alkaloids with C-2/C-7 oxidation.Their structures were characterized by a comprehensive analysis of MS,NMR,and ECD.Their effects on blood clotting times of human plasma were evaluated and alkaloid 5 had a slight prolongation effect on both thrombin time and activated partial thromboplastin time(p<0.001).

Asymmetric total synthesis of 3-epi-naucleamide A

Attempts to collective synthesis of the monoterpene indole alkaloids, isolated from Nauclea species, were examined by using asymmetric conjugate addition with Evans＇chiral auxiliary as key step. However, only the H-15 and H-3 cis product 13 was obtained, which enabled us to achieve the asymmetric total synthesis of 3-epi-naucleamide A. The results indicate that this synthetic route can be applied in the synthesis of vincosamide.

Uncarialins J-M from Uncaria rhynchophylla and Their Anti-depression Mechanism in Unpredictable Chronic Mild Stress-Induced Mice via Activating 5-HT_(1A) Receptor

Uncaria rhynchophylla has been widely used to treat central nervous system diseases for a long history.After investigation of U.rhynchophylla,eleven monoterpene indole alkaloids,including four new compounds uncarialins J-M(1-4)and seven known analogues(5-11),were isolated and identified.Their structural characterization was conducted using HRESIMS,1D and 2D NMR,electronic circular dichroism(ECD)spectra,and quantum chemical computations.Compounds 1,2,7,and 9-11 displayed significant ag-onistic effects towards 5-HT_(1A) receptor,and their EC_(50) values were 7.86,732,2.24,1.18,1.52,and 3.75μmol/L,respectively.Furthermore,in vivo experimental results fully revealed that hirsuteine(7)displayed a significant antidepression effect in unpredictable chronic mild stress(UCMS)-induced depression mice mainly via regulating 5-HT_(1A) signaling pathway.Molecular docking and site-directed amino acid mutation verified that amino acid residues Aspll6 and Asn386 were the binding sites of hirsuteine(7)with 5-HT_(1A) receptor.In addition,pre-treatment of mice with WAY 100635 also blocked the anti-depression effect of hirsuteine(7),which further demonstrated that 5-HT_(1A) receptor was a potential target of hirsuteine(7)to effectively treat depression.These findings indicated the therapeutic material basis of U.rhynchophylla and the anti-depression underlying mechanism of hirsuteine(7),and further provided the useful guidance for the development of hirsuteine(7)as a potential antidepressant candidate.