Cyclization of All-E- and 2Z-Geranylfarnesols by a Bacterial Triterpene Synthase: Insight into Sesterterpene Biosynthesis in Aleuritopteris Ferns

Aleuritopteris ferns produce triterpenes and sesterterpenes with tricyclic cheilanthane and tetracyclic 18-episcalarane skeletons. The structural and mechanistic similarities between both classes of fern terpene suggest that their biosynthetic enzymes may be closely related. We investigate here whether a triterpene synthase is capable of recognizing geranylfarnesols as a substrate, and is able to convert them to cyclic sesterterpenes. We found that a bacterial triterpene synthase converted all-E-geranylfarnesol (1b) into three scalarane sesterterpenes with 18αH stereochemistry (5, 7 and 8), as well as mono- and tricyclic sesterterpenes (6 and 9). In addition, 2Z-geranylfarnesol (4) was converted into an 18-episcalarane derivative (10), whose skeleton can be found in sesterterpenes isolated from Aleuritopteris ferns. These results provide insight into sesterterpene biosynthesis in Aleuritopteris ferns.     

Heteromerization of short-chain trans-prenyltransferase controls precursor allocation within a plastidial terpenoid network

Terpenes are the largest and most diverse class of plant specialized metabolites. Sesterterpenes(C25), which are derived from the plastid methylerythritol phosphate pathway,were recently characterized in plants. In Arabidopsis thaliana, four genes encoding geranylfarnesyl diphosphate synthase(GFPPS)(AtGFPPS1 to 4) are responsible for the production of GFPP, which is the common precursor for sesterterpene biosynthesis. However,the interplay between sesterterpenes and other known terpenes remain e...     

Overexpression of Glutathione Synthetase in Escherichia coli

Kohamaic acid A is a potent DNA polymerase inhibitor isolated from the Okinawan marine sponge Ircinia sp. A series of structurally simplified analogs of kohamaic acid A were synthesized with the aim of evaluating structure-activity relationships.     

Distinction between α- and γ-Glutamyl Dipeptides by Means of NMR Spectrometer and Amino Acid Analyzer

Conjugated metabolites of abscisic acid (ABA) have been characterized by their chemical ionization (CI) mass spectra using isobutane and ammonia as reagent gases. The CI mass spectra usually consist of quasimolecular ions ([QM]⁺), and constituent aglycone- and.sugar-derived ions. Hence, the spectra are simply interpreted and afford useful information for structutal characterization. CI examinations of ABA and its unconjugated metabolites and collisionally activated dissociation (CAD) measurements of selected ions were helpful in characterizing the constituent aglycones. The distinction between the two glycosidal forms, glycoside and glycosyl ester, has been also discussed in the corresponding conjugates. Confirmation of the fragmentation pathways via recognition of the diagnostic ions can be made by the extensive use of ammonia- d₃ as an additional reagent gas.     

丝状真菌二倍半萜化合物及其合成酶

相比其他萜类化合物,丝状真菌来源的二倍半萜化合物数量较少,但具有广泛的生理活性和药用价值。已经发现的丝状真菌二倍半萜合成酶均由萜类环化酶和异戊烯基转移酶两个结构域组成,表现出底物的非特异性和环化方式的多样性。本文重点叙述了丝状真菌来源的二倍半萜化合物以及其合成酶的结构与功能特征,并对丝状真菌二倍半萜化合物及其合成酶研究现状作简要概述。     

Unique antimicrobial spectrum of ophiobolin K produced by Aspergillus ustus

A co-cultivation study of two fungal strains showed that Aspergillus ustus could inhibit Aspergillus repens growth. The bioactive compound responsible for the observed activity was purified and identified as a sesterterpene, ophiobolin K. Ophiobolin K exhibited marked inhibition against both fungi and bacteria, especially A. repens, A. glaucus and gram-positive bacteria including Bacillus subtilis, Staphylococcus aureus, and Micrococcus luteus.