Isopentenyl pyrophosphate isomerase:dimethylallyl pyrophosphate isomerase: isolation from Claviceps sp. SD 58 and comparison to the mammalian enzyme

Isopentenyl pyrophosphate isomerase:dimethyl pyrophosphate isomerase (EC 5.3.3.2) has been purified to near homogeneity from Claviceps sp. A molecular weight of 35,000 was found by gel exclusion chromatography as well as by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This indicates that the enzyme consists of a single subunit and is in contrast to the Mr 22,000 that we have found for the enzyme from liver. The lability of isomerase from liver, often reported, has been found to be due to its susceptibility to proteolysis. Nine compounds have been tested as inhibitors of both isomerases. The binding of analogs requires the pyrophosphate moiety which may be substituted by a variety of alkyl groups. Inclusion of a polar function in the hydrocarbon portion of the analog greatly reduces interaction with the enzyme. Reversibility of the reaction was not found with a higher homolog of the substrate.     

Induced parasexual processes in Claviceps sp. strain SD58

A homokaryotic, clavine alkaloid-producing strain of ergot, Claviceps sp. strain SD 58, was used in an attempt to demonstrate parasexuality. Genetically marked auxotrophic strains were produced by mutation with N-methyl-N'-nitro-N-nitrosoguanidine. Protoplast fusion of pairs of unlike doubly auxotrophic strains and isolation of stable prototrophic fusion products were carried out. By growth of the fusion products on complete medium, selective pressure for prototrophy was removed and auxotrophic segregants were allowed to form. Analysis of these and recovery of segregants with nonleaky, non-parent-type combinations of auxotrophic characteristics has provided strong evidence that a parasexual cycle can function in Claviceps sp. strain SD 58. Preliminary work suggests that the genetics of ergot might be studied by mitotic analysis and that protoplast fusion and selection procedures might be useful for the enhancement of favorable characteristics in Claviceps strains.     

Induced parasexual processes in Claviceps sp. strain SD58.

A homokaryotic, clavine alkaloid-producing strain of ergot, Claviceps sp. strain SD 58, was used in an attempt to demonstrate parasexuality. Genetically marked auxotrophic strains were produced by mutation with N-methyl-N'-nitro-N-nitrosoguanidine. Protoplast fusion of pairs of unlike doubly auxotrophic strains and isolation of stable prototrophic fusion products were carried out. By growth of the fusion products on complete medium, selective pressure for prototrophy was removed and auxotrophic segregants were allowed to form. Analysis of these and recovery of segregants with nonleaky, non-parent-type combinations of auxotrophic characteristics has provided strong evidence that a parasexual cycle can function in Claviceps sp. strain SD 58. Preliminary work suggests that the genetics of ergot might be studied by mitotic analysis and that protoplast fusion and selection procedures might be useful for the enhancement of favorable characteristics in Claviceps strains.     

Correlation between growth and ergot alkaloid biosynthesis in Claviceps purpurea batch fermentation

Summary Following the growth kinetics of a C. purpurea ergotoxine-producing strain it was observed that alkaloid synthesis and alkaloid distribution depend on fungal growth velocity during idiophase. Formation of extracellular alkaloids is favoured by higher fungal growth velocity, while intracellular alkaloids begin to accumulate at a lower rate of growth. Simple lysergic acid derivatives prevali among extracellular alkaloids, whereas ergotoxines predominate among intracellular alkaloids. By varying cultivation conditions, by feeding the culture, or by varying the inoculum size, alkaloid composition can be influenced within the limits of strain capabilities.     

Activation of ergot alkaloid biosynthesis in prototrophic isolates by Claviceps purpurea protoplast fusion.

Intraspecific protoplast fusions were carried out with active ergocornine-ergokryptine and inactive ergocristine Claviceps purpurea strains and vice versa. The isolated prototrophic strains from both types of crosings produced all three alkaloid types, showing that biosynthesis of distinct alkaloid was activated in an inactive partner strain. The prototrophic isolates were stable on minimal medium but they segregated by subculturing on complete medium. In comparison with the original partner strains, differences in morphological and cytological characteristics were also established.     

Purification and characterization of dimethylallyl tryptophan synthase from Claviceps purpurea.

Dimethylallyl tryptophan synthase (DMAT synthase) catalyzes the alkylation of L-tryptophan by dimethylallyl diphosphate to form 4-(gamma,gamma-dimethylallyl)-L-tryptophan. The enzyme from mycelia of Claviceps purpurea was purified approximately 125-fold to apparent homogeneity by chromatography on n-butyl Sepharose, Q Sepharose, phenyl Sepharose, and Protein Pak as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Analysis by gel filtration chromatography and SDS-PAGE indicated that DMAT synthase is an alpha 2 dimer with a molecular mass of 105 kDa. The purified enzyme was active in metal-free buffer containing EDTA. However, activity was enhanced upon addition of divalent calcium or magnesium ions to the buffer. Values for KM and Vmax were determined in the metal-free EDTA buffer (KMDMAPP, 14 microM; KML-tryptophan, 40 microM; Vmax, 215 nmol min-1 mg-1), 4 mM CaCl2 (KMDMAPP, 8.0 microM; KML-tryptophan, 17 microM; Vmax, 504 nmol min-1 mg-1), and 4 mM MgCl2 (KMDMAPP, 8.0 microM; KML-tryptophan, 12 microM; Vmax, 455 nmol min-1 mg-1). The product was isolated and characterized by 1H NMR, uv, and FAB mass spectrometry.     

Purification and characterization of norcoclaurine synthase. The first committed enzyme in benzylisoquinoline alkaloid biosynthesis in plants

Norcoclaurine synthase (NCS; EC ) catalyzes the condensation of dopamine and 4-hydroxyphenylacetaldehyde (4-HPAA) as the first committed step in benzylisoquinoline alkaloid biosynthesis in plants. NCS was purified 1590-fold to homogeneity from cell suspension cultures of meadow rue (Thalictrum flavum ssp. glaucum). The purification procedure, which resulted in a 4.2% yield, involved hydrophobic interaction, anion exchange, hydroxyapatite, and gel filtration chromatography. Purified NCS displayed native and denatured molecular masses of approximately 28 and 15 kDa, respectively, suggesting that the enzyme is composed of two subunits. Two-dimensional polyacrylamide gel electrophoresis revealed two major and two minor isoforms with pI values between 5.5 and 6.2. NCS activity was maximal at pH 6.5 to 7.0 and temperatures between 42 and 55 degrees C and was not affected by divalent cations. The enzyme showed hyperbolic saturation kinetics for 4-HPAA (K(m) = 335 microm) but sigmoidal saturation kinetics for dopamine (Hill coefficient = 1.8) suggesting cooperativity between the dopamine binding sites on each subunit; thus, NCS might play a regulatory, or rate-limiting, role in controlling the rate of pathway flux in benzylisoquinoline alkaloid biosynthesis. Product inhibition kinetics performed at saturating levels of one substrate and with norlaudanosoline as the inhibitor showed that NCS follows an iso-ordered bi-uni mechanism with 4-HPAA binding before dopamine. NCS activity was highest in soluble protein extracts from roots followed by stems, leaves, and flower buds.     

Optimization of conditions for storage and cultivation of the fungus Claviceps sp.--a producer of the ergot alkaloid agroclavine

Conditions of agroclavine biosynthesis by the mutant Claviceps sp. strain s 106 were studied. The content of agroclavine was maximum (1.5-2 g/l) on days 15-16 of cultivation in the complex medium T25, containing sucrose, citric acid, and yeast extract. Agroclavine was the major component of the alkaloid fraction (90-95%). Storage of the culture at -70 degrees C in T25 supplemented by 7% glycerol provided a stable level of alkaloid formation.     

Effect of biotin on alkaloid production during submerged cultivation of Claviceps sp. strain SD-58

Addition of biotin to culture medium NL-406 significantly increased alkaloid yield during submerged cultivation of Claviceps sp. strain SD-58. Alkaloid yield was further enhanced by incorporating leucine in biotin-supplemented culture medium. Increased alkaloid production was associated with an increase in the lipid content of cells and in the number of chlamydospores. Biotin deficiency caused a reduction in alkaloid yield and a parallel decrease in lipid content and chlamydospore numbers.     

Effect of biotin on alkaloid production during submerged cultivation of Claviceps sp. strain SD-58.

Addition of biotin to culture medium NL-406 significantly increased alkaloid yield during submerged cultivation of Claviceps sp. strain SD-58. Alkaloid yield was further enhanced by incorporating leucine in biotin-supplemented culture medium. Increased alkaloid production was associated with an increase in the lipid content of cells and in the number of chlamydospores. Biotin deficiency caused a reduction in alkaloid yield and a parallel decrease in lipid content and chlamydospore numbers.     

Comparison of ergot alkaloid biosynthesis gene clusters in Claviceps species indicates loss of late pathway steps in evolution of C. fusiformis

The grass parasites Claviceps purpurea and Claviceps fusiformis produce ergot alkaloids (EA) in planta and in submerged culture. Whereas EA synthesis (EAS) in C. purpurea proceeds via clavine intermediates to lysergic acid and the complex ergopeptines, C. fusiformis produces only agroclavine and elymoclavine. In C. purpurea the EAS gene (EAS) cluster includes dmaW (encoding the first pathway step), cloA (elymoclavine oxidation to lysergic acid), and the lpsA/lpsB genes (ergopeptine formation). We analyzed the corresponding C. fusiformis EAS cluster to investigate the evolutionary basis for chemotypic differences between the Claviceps species. Other than three peptide synthetase genes (lpsC and the tandem paralogues lpsA1 and lpsA2), homologues of all C. purpurea EAS genes were identified in C. fusiformis, including homologues of lpsB and cloA, which in C. purpurea encode enzymes for steps after clavine synthesis. Rearrangement of the cluster was evident around lpsB, which is truncated in C. fusiformis. This and several frameshift mutations render CflpsB a pseudogene (CflpsB(Psi)). No obvious inactivating mutation was identified in CfcloA. All C. fusiformis EAS genes, including CflpsB(Psi) and CfcloA, were expressed in culture. Cross-complementation analyses demonstrated that CfcloA and CflpsB(Psi) were expressed in C. purpurea but did not encode functional enzymes. In contrast, CpcloA catalyzed lysergic acid biosynthesis in C. fusiformis, indicating that C. fusiformis terminates its EAS pathway at elymoclavine because the cloA gene product is inactive. We propose that the C. fusiformis EAS cluster evolved from a more complete cluster by loss of some lps genes and by rearrangements and mutations inactivating lpsB and cloA.     

Purification of S-adenosylmethionine: epsilon-N-L-lysine methyltransferase. The first enzyme in carnitine biosynthesis.

The initial steps of carnitine biosynthesis in Neurospora crassa involve the methylation of the epsilon-amino group of lysine as follows: Lysine A leads to monomethyllysine B leads to dimethyllysine C leads to trimethyllysine. The methyl donor is S-adenosylmethionine. An enzyme, S-adenosylmethionine:epsilon-N-L-lysine methyltransferase, has been purified from N. crassa to near homogeneity as judged by column chromatography, polyacrylamide gel electrophoresis, and ultracentrifugation. This protein catalyzes all three methylation reactions. The reaction rates are: A less than B less than C. Sedimentation equilibrium and molecular filtration give a molecular weight of 22,000 for the protein. Sedimentation equilibrium analysis of the protein in 6 M guanidine hydrochloride and sodium dodecyl sulfate-polyacrylamide gel electrophoresis do not detect the possibility of subunit structure. The enzyme contains no half-cystine but does contain several acidic residues. The protein exhibits an absorption band between 400 and 420 nm which is 40 to 50 times less than the absorption seen at 280 nm and is not affected by the presence of substrates. The source of this absorption in unkown.     

The ergot alkaloid gene cluster in Claviceps purpurea: extension of the cluster sequence and intra species evolution

The genomic region of Claviceps purpurea strain P1 containing the ergot alkaloid gene cluster [Tudzynski, P., H?lter, K., Correia, T., Arntz, C., Grammel, N., Keller, U., 1999. Evidence for an ergot alkaloid gene cluster in Claviceps purpurea. Mol. Gen. Genet. 261, 133-141] was explored by chromosome walking, and additional genes probably involved in the ergot alkaloid biosynthesis have been identified. The putative cluster sequence (extending over 68.5kb) contains 4 different nonribosomal peptide synthetase (NRPS) genes and several putative oxidases. Northern analysis showed that most of the genes were co-regulated (repressed by high phosphate), and identified probable flanking genes by lack of co-regulation. Comparison of the cluster sequences of strain P1, an ergotamine producer, with that of strain ECC93, an ergocristine producer, showed high conservation of most of the cluster genes, but significant variation in the NRPS modules, strongly suggesting that evolution of these chemical races of C. purpurea is determined by evolution of NRPS module specificity.     

S-Adenosyl-l-methionine: Columbamine-O-methyl transferase,a compartmentalized enzyme in protoberberine biosynthesis

Suspension cultures of Berberis wilsoniae var. subcaulialata and B. aggregata are a useful source for the detection, partial purification and characterization of a new enzyme which specifically transfers the methyl group from (S)-adenosyl-L-methionine to the 2-OH-position of columbamine, thus producing palmatine. The enzyme was enriched approx. 30-fold; it is situated in a vesicle with the density =1.14, has a pH-optimum of 8.9, a molecular weight of 52 kD and shows a high degree of substrate specificity.Abbreviations SAH S-adenosyl-L-homocysteine - SAM S-Adenosyl-L-methionine - STOX (S)-Tetrahydroprotoberberine oxidase