Anti-Allergic Effects of the Subcritical Water Extract Powder of Citrus unshiu in Mouse and Guinea Pig Models

We evaluated the effects of unripe mandarin orange (Citrus unshiu) extract powder (unripe mandarin extract powder [UMEP]) treated with subcritical water on allergic diseases by using animal models. High performance liquid chromatography (HPLC) analysis revealed that subcritical water is a more effective solvent than alcohol and hot water, as it quickly extracted approximately 90% of the functional compounds narirutin (1) and hesperidin (2) from whole fruits. Repeated oral administration of UMEP significantly reversed the peripheral blood flow decline observed during the promotion of allergies after sensitization with the antigen, hen egg-white lysozyme (HEL). UMEP also significantly inhibited compound 48/80-induced scratching behavior in HEL-sensitized mice, which are more sensitive to itching stimuli than are normal mice, without suppressing locomotor activity. In addition, repeated oral administration of UMEP in ovalbumin-challenged guinea pigs significantly suppressed the late phase of nasal airway resistance. This study provides evidence that the subcritical water extract powder of unripe C. unshiu fruit is an effective anti-allergic functional food.

5′ Untranslated region of the Hsp12 gene contributes to efficient translation in Aspergillus oryzae

We describe a 5' untranslated region (5'UTR) that dramatically increases the expression level of an exogenous gene in Aspergillus oryzae. Using a series of 5'UTR::GUS (uidA) fusion constructs, we analyzed the translation efficiency of chimeric mRNAs with different 5'UTRs at different temperatures. We found that the 5'UTR of a heat-shock protein gene, Hsp12, greatly enhanced the translation efficiency of the chimeric GUS mRNA at normal temperature (30 degrees C). Moreover, at high temperature (37 degrees C), the translation efficiency of the mRNA containing the Hsp12 5'UTR was far superior to that of mRNAs containing nonheat-shock 5'UTRs, resulting in much more efficient expression of GUS protein (about 20-fold higher GUS activity compared to the control construct). This 5'UTR can be used in combination with various strong promoters to enhance the expression of foreign proteins in A. oryzae.

High expression of a synthetic gene encoding potato alpha-glucan phosphorylase in Aspergillus niger

We describe the successful heterologous expression of the Solanum tuberosum alpha-glucan phosphorylase (GP) gene in Aspergillus niger. Special attention was paid to the influence of different codon usage and A+T content in the coding region on GP protein expression. Use of A. niger-preferred codon usage and lower A+T content in a synthetic gene (GP-syn) resulted in a significant improvement in the level of the GP mRNA and a dramatic increase in the quantity of GP protein produced such that it accounted for approximately 10% of the total soluble protein. We suggest that redesigning the primary DNA sequence encoding a desired protein product can be an extremely effective method for improving heterologous protein production in filamentous fungi.

Genome sequencing and analysis of Aspergillus oryzae

The genome of Aspergillus oryzae, a fungus important for the production of traditional fermented foods and beverages in Japan, has been sequenced. The ability to secrete large amounts of proteins and the development of a transformation system have facilitated the use of A. oryzae in modern biotechnology. Although both A. oryzae and Aspergillus flavus belong to the section Flavi of the subgenus Circumdati of Aspergillus, A. oryzae, unlike A. flavus, does not produce aflatoxin, and its long history of use in the food industry has proved its safety. Here we show that the 37-megabase (Mb) genome of A. oryzae contains 12,074 genes and is expanded by 7-9 Mb in comparison with the genomes of Aspergillus nidulans and Aspergillus fumigatus. Comparison of the three aspergilli species revealed the presence of syntenic blocks and A. oryzae-specific blocks (lacking synteny with A. nidulans and A. fumigatus) in a mosaic manner throughout the genome of A. oryzae. The blocks of A. oryzae-specific sequence are enriched for genes involved in metabolism, particularly those for the synthesis of secondary metabolites. Specific expansion of genes for secretory hydrolytic enzymes, amino acid metabolism and amino acid/sugar uptake transporters supports the idea that A. oryzae is an ideal microorganism for fermentation.

Improvement of the Aspergillus oryzae enolase promoter (P-enoA) by the introduction of cis-element repeats

We constructed a protein expression vector with an improved enoA promoter that harbored 12 tandem repeats of the cis-acting element (region III) of Aspergillus oryzae. The improved promoter yielded reporter beta-glucuronidase (GUS) activity approximately 30-fold of the original promoter. Northern blot analysis confirmed that GUS expression was increased at the transcriptional level. The transformant harboring seven copies of the novel vector showed more than 100,000 U/mg GUS protein, which was approximately 30% of all the cell-free soluble proteins.

Translation efficiency mediated by the 5' untranslated region greatly affects protein production in Aspergillus oryzae

We demonstrate that the 5' untranslated region (5'UTR) plays an important role in determining translation efficiency in Aspergillus oryzae, using a model beta-glucuronidase (GUS) expression system. Alterations in the 5' UTR resulted in an increase in GUS activity of up to eight-fold, without affecting mRNA levels. Moreover, using the most effective 5'UTR construct, we could achieve remarkable intracellular overproduction of GUS protein; and the GUS level reached more than 50% of the total soluble protein. This is the first experimental evidence indicating the feasibility of improving recombinant protein yield by promoting translation initiation in filamentous fungi.

Expression of the Fusarium oxysporum lactonase gene in Aspergillus oryzae: molecular properties of the recombinant enzyme and its application

The lactonase gene of Fusarium oxysporum was expressed in Aspergillus oryzae for optical resolution of DL-pantoyl lactone. When the chromosomal gene encoding the full-length form of the lactonase, which has its own NH2-terminal signal peptide, was introduced in the host cells, the resulting transformant produced an enzyme of 46,600 Da, which corresponded to the wild-type enzyme. In contrast, A. oryzae transformed with the cDNA coding the mature enzyme produced a protein of 41,300 Da. Deglycosylation analysis with an endoglycosidase revealed that the difference in molecular mass arose from the different sugar contents of the recombinant enzymes. The mycelia of the transformant were used as a catalyst for asymmetric hydrolysis of DL-pantoyl lactone. The initial velocity of the asymmetric hydrolysis reaction catalyzed by the transformant was estimated to be 30 times higher than that by F. oxysporum. When the mycelia of the transformant were incubated with a 20% DL-pantoyl lactone solution for 4 h, 49.9% of the racemic mixture was converted to D-pantoic acid (>95% ee).

Deletion analysis of the enolase gene (enoA) promoter from the filamentous fungus Aspegillus oryzae

The enolase gene (enoA) is one of the most strongly expressed genes in Aspergillus oryzae. To elucidate the transcription regulatory element for this strong expression and the process of glucose induction, the transcription activity of a series of truncated enoA promoters was measured by using the Escherichia coli uidA gene as a reporter. Deletion of a 104-bp region located -224 nt to -121 nt upstream of the translation initiation site caused both a drastic decrease in the beta-glucuronidase (GUS) activity and a loss of glucose induction. Northern blot analysis confirmed that the decrease in GUS activity was achieved at the transcriptional level. In addition, electrophoretic gel mobility shift assays indicated that the 104-bp region contained a 15-bp element, to which one or more A. oryzae cellular factors specifically bind. These results suggest that the 15-bp element between -195 nt and -181 nt includes the sequence essential for the transcription regulation of the A. oryzae enoA gene.

Molecular cloning and characterization of a transcriptional activator gene, amyR, involved in the amylolytic gene expression in Aspergillus oryzae

A gene, designated amyR, coding for a transcriptional activator involved in amylolytic gene expression has been cloned from Aspergillus oryzae by screening for a clone that enabled to reverse the reduced expression of the alpha-amylase gene (amyB) promoter. amyR encodes 604 amino acid residues of a putative DNA-binding protein carrying a zinc binuclear cluster motif (Zn(II)2Cys6) belonging to the GAL4 family of transcription factors. The amyR gene disruptants showed a significant restricted growth on starch medium and produced little of the amylolytic enzymes including alpha-amylase and glucoamylase compared with a non-disruptant, indicating that amyR is a transcriptional activator gene involved in starch/maltose-induced efficient expression of the amylolytic genes in A. oryzae. In addition, sequencing analysis found that amyR, agdA (encoding alpha-glucosidase), and amyA (encoding alpha-amylase), are clustered on a 12-kb DNA fragment of the largest chromosome in A. oryzae, and that amyR is about 1.5 kb upstream of agdA and transcribed in the opposite direction. Furthermore, transcriptional analysis revealed that the amyR gene was expressed in the presence of glucose comparable to the level in the presence of maltose, while the amylolytic genes were transcribed at high levels only in the presence of maltose.

Rapid detection of homologously integrated DNA fragments and accurate quantitation of their copy number in transgenic Aspergillus oryzae by PCR

A simple and rapid method for the analysis of artificially introduced DNA fragments has been developed using competitive PCR and long and accurate PCR. The locus and the copy number of the DNA fragments in each Aspergillus oryzae transformant could be detected more rapidly and accurately by this method than by the conventional Southern hybridization method.

Molecular and enzymic properties of recombinant 1, 2-alpha-mannosidase from Aspergillus saitoi overexpressed in Aspergillus oryzae cells

For the construction of an overexpression system of the intracellular 1,2-alpha-mannosidase (EC 3.2.1.113) gene (msdS) from Aspergillus saitoi (now designated Aspergillus phoenicis), the N-terminal signal sequence of the gene was replaced with that of the aspergillopepsin I (EC 3.4.23.18) gene (apnS) signal, one of the same strains as described previously. Then the fused 1, 2-alpha-mannosidase gene (f-msdS) was inserted into the NotI site between P-No8142 and T-agdA in the plasmid pNAN 8142 (9.5 kbp) and thus the Aspergillus oryzae expression plasmid pNAN-AM1 (11.2 kbp) was constructed. The fused f-msdS gene has been overexpressed in a transformant A. oryzae niaD AM1 cell. The recombinant enzyme expressed in A. oryzae cells was purified to homogeneity in two steps. The system is capable of making as much as about 320 mg of the enzyme/litre of culture. The recombinant enzyme has activity with methyl-2-O-alpha-d-mannopyranosyl alpha-D-mannopyranoside at pH 5.0, while no activity was determined with methyl-3-O-alpha-D-mannopyranosyl alpha-D-mannopyranoside or methyl-6-O-alpha-D-mannopyranosyl alpha-D-mannopyranoside. The substrate specificity of the enzyme was analysed by using pyridylaminated (PA)-oligomannose-type sugar chains, Man9-6(GlcNAc)2-PA (Man is mannose; GlcNAc is N-acetylglucosamine). The enzyme hydrolysed Man8GlcNAc2-PA (type 'M8A') fastest, and 'M6C' {Manalpha1-3[Manalpha1-2Manalpha1-3(Manalpha1-6) Manalpha1-6]Manbeta1- 4GlcNAcbeta1-4GlcNAc-PA} slowest, among the PA-sugar chains. Molecular-mass values of the enzyme were determined to be 63 kDa by SDS/PAGE and 65 kDa by gel filtration on Superose 12 respectively. The pI value of the enzyme was 4.6. The N-terminal amino acid sequence of the enzyme was GSTQSRADAIKAAFSHAWDGYLQY, and sequence analysis indicated that the signal peptide from apnS gene was removed. The molar absorption coefficient, epsilon, at 280 nm was determined as 91539 M-1.cm-1. Contents of the secondary structure (alpha-helix, beta-structure and the remainder of the enzyme) by far-UV CD determination were about 55, 38 and 7% respectively. The melting temperature, Tm, of the enzyme was 71 degrees C by differential scanning calorimetry. The calorimetric enthalpy, DeltaHcal, of the enzyme was calculated as 13.3 kJ.kg of protein-1. Determination of 1 g-atom of Ca2+/mol of enzyme was performed by atomic-absorption spectrophotometry.

Improvement of promoter activity by the introduction of multiple copies of the conserved region III sequence, involved in the efficient expression of Aspergillus oryzae amylase-encoding genes

The role of the conserved sequence region III in the promoter regions of the amylase-encoding genes amyB, glaA and agdA of Aspergillus oryzae was examined. Introduction of multiple copies of the region III fragment into the agdA promoter resulted in a significant increase in promoter activity at the transcriptional level. This result suggests that the fragment comprising region III consists of one or more cis-acting sequence(s). Moreover, expression of the agdA gene under the control of the improved agdA promoter resulted in efficient overproduction of alpha-glucosidase, even in the presence of glucose. Thus, overexpression of genes controlled by the improved promoter incorporating region III is possible. Interestingly, expression of the amyB and glaA genes in the transformant was strongly repressed. This result suggests that the trans-acting regulatory protein(s) that interact with region III are common to these amylase genes and that the titration of regulatory protein(s) reduced the expression of the amyB and glaA genes.

Deletion analysis of promoter elements of the Aspergillus oryzae agdA gene encoding alpha-glucosidase

The nucleotide sequence of a 1.5-kb fragment of the promoter region of the Aspergillus oryzae agdA gene encoding alpha-glucosidase was determined. A comparison with the promoter regions of other Aspergillus amylase genes indicated that there are three highly conserved sequences, designated Regions I, II and III, located at -670 nt, -596 nt and -544 nt relative to the start codon, respectively. The function of these consensus sequences in the agdA promoter was investigated by deletion analysis of a promoter fusion with the Escherichia coli uidA gene, using the niaD homologous-transformation system. Deletion of the upstream half of Region III (IIIa; -544 to -529) resulted in a more than 90% reduction in GUS activity and abolished maltose induction, suggesting that Region IIIa is a functionally essential element for high-level expression and maltose induction. Deletion of Region I and the downstream half of Region III (IIIb; -521 to -511) resulted in a significant reduction in GUS activity, but did not affect maltose induction. This suggested that these two elements most likely contain sequences involved in efficient expression in cooperation with Region IIIa. In addition, deletion of a 340-bp region between Region IIIb and the putative TATA box resulted in a 2-fold increase in activity.

Characteristic expression of three amylase-encoding genes, agdA, amyB, and glaA in Aspergillus oryzae transformants containing multiple copies of the agdA gene

In Aspergillus oryzae wild-type strains, the expression of the agdA gene encoding alpha-glucosidase (AGL) is induced by maltose at the transcriptional level in a similar manner to the amyB gene encoding Takaamylase A (TAA) and the glaA gene encoding glucoamylase (GLA). In A. oryzae transformants containing multiple copies of the agdA gene, a high-level of AGL activity was observed. This was accompanied by a significant reduction in TAA and GLA activities. Moreover, transformants with the highest AGL activity showed the lowest degree of TAA and GLA activities. Northern blot analyses showed that the transcriptional levels of amyB and glaA in the AGL-overproducing transformant were drastically reduced when large amounts of agdA mRNA were detected in maltose-grown mycelia. In addition, the glucose concentration of the maltose-containing medium that was used to grow the AGL-overproducing transformant for RNA extraction was higher than that of the control transformant. These results suggest that the reduced expression of the amyB and glaA genes in the AGL-overproducing transformant was due to either titration of a common regulatory protein(s) involved in maltose induction or carbon catabolite repression.

Nucleotide sequence and expression of alpha-glucosidase-encoding gene (agdA) from Aspergillus oryzae

We have isolated an alpha-glucosidase(AGL)-encoding gene (agdA) from Aspergillus oryzae by heterologous hybridization using the corresponding Aspergillus niger gene as a probe. Southern hybridization analysis showed that the agdA gene is on a 5.0-kb ScaI fragment and there is a single copy in the A. oryzae chromosome. Comparison with the A. niger agdA gene indicated that the agdA gene contains three putative introns from 52 to 59 nucleotides long, and that it encodes 985 amino acid residues. The deduced amino acid sequence of A. oryzae AGL is 78% homologous with the A. niger AGL. The high degree of homology with the amino acid sequence bordering the putative catalytic residue of a number of AGL enzymes, and this enzyme suggests that Asp492 is a catalytic residue of A. oryzae AGL. The cloned gene was functional. Transformants of A. oryzae containing multiple copies of the cloned agdA gene showed a 6-16 fold increase in AGL activity. Like the Taka-amylase A and glucoamylase genes of A. oryzae, expression of the agdA gene was induced when maltose was provided as a carbon source, but expression was not induced by glucose. This result suggested that cis-element(s) involved in maltose induction may be also present in the agdA promoter region.

The purification, properties and internal peptide sequences of alcohol acetyltransferase isolated from Saccharomyces cerevisiae Kyokai No. 7

Alcohol acetyltransferase (AATase) catalyzes the esterification of isoamyl alcohol by acetyl coenzyme A. The enzyme was solubilized from the microsomal fraction of Saccharomyces cerevisiae Kyokai No. 7, using Triton X-100 and then purified by a series of chromatographic separations: Poly Buffer Exchanger 94 (PBE94), DEAE Toyopearl, Toyopearl HW60, hydroxyapatite, Octyl-Sepharose CL-4B, and hexanol-affinity column chromatography. When the solubilized enzyme was put on PBE94, two active fractions were obtained. The enzyme obtained after affinity column chromatography had a single band on an SDS polyacrylamide gel, and its molecular mass was estimated to be 60 kDa. The enzyme was most active at pH 8.0 and 25 degrees C. It was stable between pH 7.5 and 8.5, but was unstable at temperatures above 10 degrees C. The activity was markedly inhibited by heavy metal ions such as Cd2+, Cu2+, Zn2+, and Hg2+, and sulfhydryl reagents. The Km for acetyl-CoA was 0.19 mM. The internal peptide sequences were also identified.

Molecular cloning and nucleotide sequence of the gramicidin S synthetase 1 gene

The entire gene for gramicidin S synthetase 1 (GS 1) was cloned into the plasmid vector pUC18, and the nucleotide sequences of the GS 1 gene and its flanking region were determined. The full-length clone was 4,539 base pairs long and had an open reading frame of 3,294 nucleotides coding for 1,098 amino acids. The calculated molecular weight of 123,474 agreed with the apparent molecular weight of 120,000 found in SDS-PAGE of GS 1 from B. brevis. The nucleotide sequence of GS 1 gene was highly homologous to that of tyrocidine synthetase 1. The overall similarity between the deduced amino acid sequences of the two genes was 57.5%. The gene product of clone GS309 was easily purified to an essentially homogeneous state by ammonium sulfate fractionation followed by DEAE-Sepharose CL-6B, Ultrogel AcA-34, and second DEAE-Sepharose CL-6B column chromatography. The purified protein catalyzed the D-phenylalanine-dependent ATP-32PPi exchange reaction which is specific for GS 1 activity, and the specific activity of the purified product was nearly the same as the purified GS 1 from B. brevis. The product also showed a weak phenylalanine racemase activity.