No abstract

In microorganisms, menaquinone is an obligatory component of the electron-transfer pathway. It is derived from chorismate by seven enzymes in Escherichia coli. However, a bioinformatic analysis of whole genome sequences has suggested that some microorganisms, including pathogenic species such as Helicobacter pylori and Campylobacter jejuni, do not have orthologs of the men genes, even though they synthesize menaquinone. We deduced the outline of this alternative pathway in a nonpathogenic strain of Streptomyces by bioinformatic screening, gene knockouts, shotgun cloning with isolated mutants, and in vitro studies with recombinant enzymes. As humans and commensal intestinal bacteria, including lactobacilli, lack this pathway, it represents an attractive target for the development of chemotherapeutics.

Parkinson disease (PD) is a neurodegenerative disorder characterized by loss of midbrain dopaminergic (DA) neurons. ES cells are currently the most promising donor cell source for cell-replacement therapy in PD. We previously described a strong neuralizing activity present on the surface of stromal cells, named stromal cell–derived inducing activity (SDIA). In this study, we generated neurospheres composed of neural progenitors from monkey ES cells, which are capable of producing large numbers of DA neurons. We demonstrated that FGF20, preferentially expressed in the substantia nigra, acts synergistically with FGF2 to increase the number of DA neurons in ES cell–derived neurospheres. We also analyzed the effect of transplantation of DA neurons generated from monkey ES cells into 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine–treated (MPTP-treated) monkeys, a primate model for PD. Behavioral studies and functional imaging revealed that the transplanted cells functioned as DA neurons and attenuated MPTP-induced neurological symptoms

Styrene monooxygenase (SMO) is a two-component flavoprotein catalyzing the selective epoxidation of various CC double bonds. For cell-free catalysis, traditionally a cascade of NAD­(P)­H:flavin oxidoreductase, nicotinamide cofactor (NADH), and NADH regeneration enzyme is required to supply StyA with the reduced flavin adenine dinucleotide cofactor (FADH2) required for catalysis. Herein, we present a more direct and efficient FADH2 regeneration system using the nicotinamide cofactor mimic 1-benzyl-1,4-dihydronicotinamide (BNAH) as the sole reductant. Thus, BNAH replaces two enzymes and the nicotinamide cofactor, resulting in a significantly simplified reaction system.

). Sequence analysis in the upstream region of the cluster revealed seven new ORFs, ORF8 to ORF14, which were suggested to encode TP biosynthetic genes. We constructed two mutants, in which ORF11 and ORF12, which encode a protein showing similarities to eukaryotic diterpene cyclases (DCs) and a eubacterial pentalenene synthase, respectively, were inactivated by gene disruptions. The mutants produced no TP, confirming that these cyclase genes are essential for the production of TP. The two cyclase genes were also expressed in Streptomyces lividans together with the GGDP synthase gene under the control of the ermE* constitutive promoter. The transformant produced a novel cyclic diterpenoid, ent-clerod-3,13(16),14-triene (terpentetriene), which has the same basic skeleton as TP. The two enzymes, each of which was overproduced in Escherichia coli and purified to homogeneity, converted GGDP into terpentetriene. To the best of our knowledge, this is the first report of a eubacterial DC.Isoprenoids are the largest single family of compounds found in nature, with over 22,000 known examples (12), and can be classified into several groups based on the number of C 5 units derived from isopentenyl diphosphate (IPP), such as monoterpenes (C 10 ), sesquiterpenes (C 15 ), diterpenes (C 20 ), and triterpenes (C 30 ), etc. (12). These compounds are biosynthesized from the corresponding prenyl diphosphate. Geranyl diphosphate gives rise to monoterpenes, farnesyl diphosphate gives rise to sesquiterpenes, and geranylgeranyl diphosphate (GGDP) gives rise to diterpenes (9, 29) (Fig. 1). In many cases, these prenyl diphosphates undergo a range of cyclizations to produce the parent skeletons of each class, followed by a variety of modifications to give many thousands of different isoprenoid metabolites (9, 29).A variety of isoprenoid synthases (cyclases), most of which are from plants and fungi, have been purified and extensively studied (12). As for the genes encoding isoprenoid cyclases, more than 30 eukaryotic isoprenoid synthases have been cloned as cDNAs (9, 29). On the other hand, there have been few reports about eubacterial isoprenoid cyclases and genes because the vast majority of isoprenoids are produced by eukaryotes. Pentalenene synthase, a sesquiterpene cyclase from a Streptomyces strain (10), and squalene-hopene cyclases, triterpene cyclases from bacteria, are the only examples (22,32,34,35,42,46). There are no reports, to the best of our knowledge, about eubacterial monoterpene cyclases and diterpene cyclases (DCs).We have been studying the biosynthesis of isoprenoid antibiotics produced by actinomycetes. Although actinomycetes produce approximately 70% of all natural compounds, a very limited number of isoprenoid compounds are known to be produced by them (30). The gene cluster containing the mevalonate pathway genes used to synthesize IPP had previously been cloned from Streptomyces griseolosporeus strain MF730-N6, a diterpene antibiotic terpentecin (TP) producer (15). The GGDP synthase gene encoding the enzyme catalyz...

Furaquinocin (FQ) A, produced by Streptomyces sp. strain KO-3988, is a natural polyketide-isoprenoid hybrid compound that exhibits a potent antitumor activity. As a first step toward understanding the biosynthetic machinery of this unique and pharmaceutically useful compound, we have cloned an FQ A biosynthetic gene cluster by taking advantage of the fact that an isoprenoid biosynthetic gene cluster generally exists in flanking regions of the mevalonate (MV) pathway gene cluster in actinomycetes. Interestingly, Streptomyces sp. strain KO-3988 was the first example of a microorganism equipped with two distinct mevalonate pathway gene clusters. We were able to localize a 25-kb DNA region that harbored FQ A biosynthetic genes (fur genes) in both the upstream and downstream regions of one of the MV pathway gene clusters (MV2) by using heterologous expression in Streptomyces lividans TK23. This was the first example of a gene cluster responsible for the biosynthesis of a polyketide-isoprenoid hybrid compound. We have also confirmed that four genes responsible for viguiepinol [3-hydroxypimara-9(11),15-diene] biosynthesis exist in the upstream region of the other MV pathway gene cluster (MV1), which had previously been cloned from strain KO-3988. This was the first example of prokaryotic enzymes with these biosynthetic functions. By phylogenetic analysis, these two MV pathway clusters were identified as probably being independently distributed in strain KO-3988 (orthologs), rather than one cluster being generated by the duplication of the other cluster (paralogs).

Eubacterial diterpene cyclase genes had previously been cloned from a diterpenoid antibiotic terpentecin producer (Dairi, T., Hamano, Y., Kuzuyama, T., Itoh, N., Furihata, K., and Seto, H. (2001) J. Bacteriol. 183, 6085-6094). Their products, open reading frame 11 (ORF11) and ORF12, were essential for the conversion of geranylgeranyl diphosphate (GGDP) into terpentetriene (TTE) that had the same basic skeleton as terpentecin. In this study, functional analyses of these two enzymes were performed by using purified recombinant enzymes. The ORF11 product converted GGDP into a cyclized intermediate, terpentedienol diphosphate (TDP), which was then transformed into TTE by the ORF12 product. Interestingly, the ORF12 product directly catalyzed the conversion of GGDP into three olefinic compounds. Moreover, the ORF12 product utilized farnesyl diphosphate as a substrate to give three olefinic compounds, which had the same structures as those formed from GGDP with the exception of the chain lengths. These results suggested that the ORF11 product with a DXDD motif converted GGDP into TDP by a protonation-initiated cyclization and that the ORF12 product with a DDXXD motif completed the transformation of TDP to the olefin, terpentetriene by an ionization-initiated reaction followed by deprotonation. The kinetics of the ORF12 product indicated that the affinity for TDP and GGDP were higher than that of farnesyl diphosphate and that the relative activity of the reaction converting TDP into TTE was highest among the reactions using TDP, GGDP, or farnesyl diphosphate as the substrate. These results suggested that an actual reaction catalyzed by the ORF12 was the conversion of TDP into TTE in vivo.

Background: Biogenic emissions of methyl halides (CH 3 Cl, CH 3 Br and CH 3 I) are the major source of these compounds in the atmosphere; however, there are few reports about the halide profiles and strengths of these emissions. Halide ion methyltransferase (HMT) and halide/thiol methyltransferase (HTMT) enzymes concerning these emissions have been purified and characterized from several organisms including marine algae, fungi, and higher plants; however, the correlation between emission profiles of methyl halides and the enzymatic properties of HMT/ HTMT, and their role in vivo remains unclear.