Cloning of a phenol oxidase gene from Acremonium murorum and its expression in Aspergillus awamori

The heme binding protein ChuX is a regulator of heme degradation by the ChuS protein in Escherichia coli O157:H7

Escherichia coli O157:H7 possesses an 8-gene cluster (chu genes) that contains genes involved in heme transport and processing from the human host. Among the chu genes, four encode cytoplasmic proteins (ChuS, ChuX, ChuY and ChuW). ChuX was previously shown to be a heme binding protein and to assist ChuW in heme degradation under anaerobic conditions. The purpose of this work was to investigate if ChuX works in concert with ChuS, which is a protein able to degrade heme by a non-canonical mechanism and release the iron from the porphyrin under aerobic conditions using hydrogen peroxide as the oxidant. We showed that when the heme-bound ChuX and apo-ChuS protein are mixed, heme is efficiently transferred from ChuX to ChuS. Heme-bound ChuX displayed a peroxidase activity with ABTS and H2O2 but not heme-bound ChuS, which is an efficient test to determine the protein to which heme is bound in the ChuS-ChuX complex. We found that ChuX protects heme from chemical oxidation and that it has no heme degradation activity by itself. Unexpectedly, we found that ChuX inhibits heme degradation by ChuS and stops the reaction at an early intermediate. We determined using surface plasmon resonance that ChuX interacts with ChuS and that it forms a relatively stable complex. These results indicate that ChuX in addition to its heme transfer activity is a regulator of ChuS activity, a function that was not described before for any of the heme carrier protein that delivers heme to heme degradation enzymes.

Unusual Oligomeric Laccase-like Oxidases from Ascomycete Curvularia geniculata VKM F-3561 Polymerizing Phenylpropanoids and Phenolic Compounds under Neutral Environmental Conditions

The unique oligomeric alkaliphilic laccase-like oxidases of the ascomycete C. geniculata VKM F-3561 (with molecular masses about 1035 and 870 kDa) were purified and characterized for the first time. The ability of the enzymes to oxidize phenylpropanoids and phenolic compounds under neutral environmental conditions with the formation of previously unknown di-, tri-, and tetrameric products of transformation was shown. The possibility to obtain industrially valuable compounds (dihydroxybenzyl alcohol and hydroxytyrosol) from caffeic acid using laccase-like oxidases of C. geniculata VKM F-3561 has been shown. Complete nucleotide sequence of the laccase gene, which is expressed at the peak of alkaliphilic laccase activity of the fungus, and its promoter region were determined. Based on the phylogenetic analysis of the nucleotide sequence, the nearest relationship of the isolated laccase gene with similar genes of fungi of the genera Alternaria, Bipolaris, and Cochliobolus was shown. Homologous model of the laccase structure was predicted and a proton channel was found, which was presumably responsible for the accumulation and transport of protons to T2/T3-copper center in the alkaliphilic laccase molecule and providing the functional activity of the enzyme in the neutral alkaline environment conditions.

The Laccase of Myrothecium roridum VKM F-3565: A New Look at Fungal Laccase Tolerance to Neutral and Alkaline Conditions

Most of the currently known fungal laccases show their maximum activity under acidic environmental conditions. It is known that a decrease in the activity of a typical laccase at neutral or alkaline pH values is the result of an increase in the binding of the hydroxide anion to the T2/T3 copper center, which prevents the transfer of an electron from the T1 Cu to the trinuclear copper center. However, evolutionary pressure has resolved the existing limitations in the catalytic mechanism of laccase, allowing such enzymes to be functionally active under neutral/alkaline pH conditions, thereby giving fungi an advantage for their survival. Combined molecular and biochemical studies, homological modeling, calculation of the electrostatic potential on the Connolly surface at pH 5.0 and 7.0, and structural analysis of the novel alkaliphilic laccase of Myrothecium roridum VKM F-3565 and alkaliphilic and acidophilic fungal laccases with a known structure allowed a new intramolecular channel near the one of the catalytic aspartate residues at T2-copper atom to be found. The amino acid residues of alkaliphilic laccases forming this channel can presumably serve as proton donors for catalytic aspartates under neutral conditions, thus ensuring proper functioning. For the first time for ascomycetous laccases, the production of new trimeric products of phenylpropanoid condensation under neutral conditions has been shown, which could have a potential for use in pharmacology.

Analysis of laccase‐like enzymes secreted by fungi isolated from a cave in northern Spain

Laccases belong to a family of multicopper enzymes able to oxidize a broad spectrum of organic compounds. Despite the well‐known property of laccases to carry out bleaching and degradation of industrial dyes and polyphenolic compounds, their industrial use is often limited by the high cost, low efficiency, or instability of these enzymes. To look for new microorganisms which produce laccases that are potentially suitable for industrial applications, we have isolated several fungal strains from a cave in northern Spain. Their phenotypic analysis on agar plates supplemented with ABTS (2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid)) disclosed two laccase‐positive strains. Further genotyping revealed that they belonged to the Gliomastix murorum and Conidiobolus thromboides species. The secretion of G. murorum and C. thromboides laccase‐like enzymes was then confirmed by zymography. Further identification of these polypeptides by mass‐spectroscopy revealed the nature of the laccases and made it possible to predict their functional domains and other features. In addition, plate assays revealed that the laccases secreted by both G. murorum and C. thromboides were capable of degrading industrial dyes (Congo Red, Indigo, and Eriochrome Black T). Homology modeling and substrate docking predicted the putative structure of the currently uncrystallized G. murorum enzyme as well as its amino acid residues potentially involved in interactions with these dyes. In summary, new biochemical and structural insights into decolorization mediated by G. murorum laccase as well as identification of laccase‐like oxidase in C. thromboides point to a promising future for these enzymes in biotechnology.

Properties of the newly isolated extracellular thermo-alkali-stable laccase from thermophilic actinomycetes, Thermobifida fusca and its application in dye intermediates oxidation

Laccases are diphenol oxidases that have numerous applications to biotechnological processes. In this study, the laccase was produced from the thermophilic actinomycetes, Thermobifida fusca BCRC 19214. After 36 h of fermentation in a 5-liter fermentor, the culture broth accumulated 4.96 U/ml laccase activity. The laccase was purified 4.64-fold as measured by specific activity from crude culture filtrate by ultrafiltration concentration, Q-Sepharose FF and Sephacryl™ S-200 column chromatography. The overall yield of the purified enzyme was 7.49%. The molecular mass of purified enzyme as estimated by SDS-PAGE and by gel filtration on Sephacryl™ S-200 was found to be 73.3 kDa and 24.7 kDa, respectively, indicating that the laccase from T. fusca BCRC 19214 is a trimer. The internal amino acid sequences of the purified laccase, as determined by LC-MS/MS, had high homology with a superoxide dismutase from T. fusca YX. Approximately 95% of the original activity remained after treatment at 50°C for 3 h. and approximately 75% of the original activity remained after treatment at pH 10.0 for 24 h. This laccase could oxidize dye intermediates, especially 2,6-dimethylphenylalanine and p-aminophenol, to produce coloring. This is the first report on laccase properties from thermophilic actinomycetes. These properties suggest that this newly isolated laccase has potential for specific industrial applications.

Electrochemical characterization of a unique, "neutral" laccase from Flammulina velutipes

The flac1 gene consisted of 1488 bases encodes a novel laccase (Flac1) from Flammulina velutipes. The deduced amino acid sequence of Flac1 with 496 amino acids shows 58-64% homologies with other fungal laccases. The recombinant Flac1 (rFlac1) was heterologously expressed in Pichia pastoris, with sugars of approximately 4 kDa attached on the protein molecule, which has the calculated molecular mass of 53,532 Da. rFlac1 was shown to be a multi-copper oxidase from spectroscopies. The optimum pHs of rFlac1 for oxidations of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), p-phenylenediamine, and o-aminophenol, were 5.0, 5.0, and 6.0-6.5, respectively, showing higher pH values than those from many other fungal laccases. The slightly acidic or neutral optimum pH that is not strongly dependent on substrates is a unique property of rFlac1. Effective O(2) reduction was realized by the direct electron transfer of rFlac1 at a highly oriented pyrolytic graphite electrode modified with fine carbon particles (Ketjen Black) in O(2)-saturated solution. The pHs showing the maximum ΔE°' [=E°'(enzyme) - E°'(substrate)] coincided well with the optimum pHs shown by rFlac1 under steady-state conditions. The present electrochemical results of rFlac1 indicate that ΔE°' is one of the primary factors to determine the activity of multi-copper oxidases.

LccA, an archaeal laccase secreted as a highly stable glycoprotein into the extracellular medium by Haloferax volcanii

Laccases couple the oxidation of phenolic compounds to the reduction of molecular oxygen and thus span a wide variety of applications. While laccases of eukaryotes and bacteria are well characterized, these enzymes have not been described in archaea. Here, we report the purification and characterization of a laccase (LccA) from the halophilic archaeon Haloferax volcanii. LccA was secreted at high levels into the culture supernatant of a recombinant H. volcanii strain, with peak activity (170 +/- 10 mU.ml(-)(1)) at stationary phase (72 to 80 h). LccA was purified 13-fold to an overall yield of 72% and a specific activity of 29.4 U.mg(-)(1) with an absorbance spectrum typical of blue multicopper oxidases. The mature LccA was processed to expose an N-terminal Ala after the removal of 31 amino acid residues and was glycosylated to 6.9% carbohydrate content. Purified LccA oxidized a variety of organic substrates, including bilirubin, syringaldazine (SGZ), 2,2,-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and dimethoxyphenol (DMP), with DMP oxidation requiring the addition of CuSO(4). Optimal oxidation of ABTS and SGZ was at 45 degrees C and pH 6 and pH 8.4, respectively. The apparent K(m) values for SGZ, bilirubin, and ABTS were 35, 236, and 670 muM, with corresponding k(cat) values of 22, 29, and 10 s(-)(1), respectively. The purified LccA was tolerant of high salt, mixed organosolvents, and high temperatures, with a half-life of inactivation at 50 degrees C of 31.5 h.

Microbial manganese oxide formation and interaction with toxic metal ions

Diverse bacteria and fungi oxidize Mn(II) enzymatically and produce insoluble Mn(III, IV) oxides, and these organisms are considered to be the primal agents for the occurrence of natural Mn oxide phases in most environments. Biogenic Mn oxides have a high sorption capacity for metal cations and an ability to oxidize numerous inorganic and organic compounds, owing to their structural and redox features. Thus, the microbial process is of significance in both biogeochemical and biotechnological contexts. In this article we summarize the enzymatic Mn(II) oxidation and interactions of biogenic Mn oxides with toxic metal and metalloid ions. Although Mn oxide formation by fungi has not been fully characterized yet, recent researches with ascomycetes emphasize the similarity between the bacterial and fungal Mn(II) oxidation with respect to the involved catalyst (i.e., multicopper oxidase-type enzymes) and the reaction product [i.e., layer-type Mn(IV) oxides]. Laboratory cultures of bacterial and fungal Mn oxidizers are expected to provide fundamental knowledge in their potential use for remediation of environments and effluents contaminated with toxic metal(loid) ions.

Electrochemical consideration on the optimum pH of bilirubin oxidase

Steady-state current-potential curves were obtained for the direct electron transfer (DET) of bilirubin oxidase (BOD) at a highly oriented pyrolytic graphite electrode, and the theoretical analysis based on nonlinear regression enabled us to determine the formal redox potential (E degrees') of BOD in a wide pH range of 2.0 to 8.5. Cyclic voltammetric measurements were also performed for substrates, including p-phenylenediamine (PPD), o-aminophenol (OAP), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and their E degrees ' values or the anodic peak potentials (for OAP) were determined at various pH values. The difference in the redox potentials between BOD and substrates (DeltaE degrees') showed a maximum at pH 6.5 to 8.0, pH 6.5 to 8.0, and pH 3.5 to 4.5 for PPD, OAP, and ABTS, respectively. These pH ranges should be thermodynamically most favorable for the electron transfer between BOD and the respective substrates. In practice, the pH ranges showing a maximum DeltaE degrees' corresponded well with the optimum pH values for the O(2) reduction activity of BOD: pH 6.5 to 7.5, pH 8.0 to 8.5, and pH 4.0 for PPD, OAP, and ABTS, respectively. Thus, it was suggested that DeltaE degrees ' should be one of the primary factors determining the activity of BOD with the substrates.

High production of laccase by a new basidiomycete, Trametes sp

A new basidiomycete, Trametes sp. 420, produced laccase at 6,810 U l(-1) (268 mg, 25.4 U mg(-1) protein for guaiacol) in glucose medium and 7,870 U l(-1) (310 mg) in cellobiose medium with induction by 0.5 mM Cu(2+) and 6 mM o-toluidine. Laccase isozyme E (LacE) was the sole laccase in the fermentation products. It was stable at pH 5-9 and below 70 degrees C over 30 min. The K (m) values of LacE for four substrates (guaiacol ABTS, 2,6-dimethoxyphenol and syringaldazine) varied from 5 to 245 muM. The activity of LacE was strongly inhibited by NaN(3) but not by EDTA or dimethylsulfoxide. LacE at 0.5 U l(-1) could decolorize industrial dyes. The open reading frame of the lacE gene was 2,130 bp and was interrupted by 10 introns. It displayed a high homology to laccases from other fungi.

Manganese(IV) oxide production by Acremonium sp. strain KR21-2 and extracellular Mn(II) oxidase activity

Ascomycetes that can deposit Mn(III, IV) oxides are widespread in aquatic and soil environments, yet the mechanism(s) involved in Mn oxide deposition remains unclear. A Mn(II)-oxidizing ascomycete, Acremonium sp. strain KR21-2, produced a Mn oxide phase with filamentous nanostructures. X-ray absorption near-edge structure (XANES) spectroscopy showed that the Mn phase was primarily Mn(IV). We purified to homogeneity a laccase-like enzyme with Mn(II) oxidase activity from cultures of strain KR21-2. The purified enzyme oxidized Mn(II) to yield suspended Mn particles; XANES spectra indicated that Mn(II) had been converted to Mn(IV). The pH optimum for Mn(II) oxidation was 7.0, and the apparent half-saturation constant was 0.20 mM. The enzyme oxidized ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] (pH optimum, 5.5; Km, 1.2 mM) and contained two copper atoms per molecule. Moreover, the N-terminal amino acid sequence (residues 3 to 25) was 61% identical with the corresponding sequence of an Acremonium polyphenol oxidase and 57% identical with that of a Myrothecium bilirubin oxidase. These results provide the first evidence that a fungal multicopper oxidase can convert Mn(II) to Mn(IV) oxide. The present study reinforces the notion of the contribution of multicopper oxidase to microbially mediated precipitation of Mn oxides and suggests that Acremonium sp. strain KR21-2 is a good model for understanding the oxidation of Mn in diverse ascomycetes.

Extracellular production of neoculin, a sweet-tasting heterodimeric protein with taste-modifying activity, by Aspergillus oryzae

Neoculin (NCL), a protein with sweetness approximately 500-fold that of sugar, can be utilized as a nonglycemic sweetener. It also has taste-modifying activity to convert sourness to sweetness. NCL is a heterodimer composed of an N-glycosylated acidic subunit (NAS) and a basic subunit (NBS), which are conjugated by disulfide bonds. For the production of recombinant NCL (rNCL) by Aspergillus oryzae, alpha-amylase with a KEX2 cleavage site, -K-R-, was fused upstream of each of NAS and NBS and the resulting fusion proteins were simultaneously expressed. For accurate and efficient cleavage of the fusion construct by KEX2-like protease, a triglycine motif was inserted after the KEX2 cleavage site. As NBS showed lower production efficiency than did NAS, a larger amount of the NBS expression plasmid than of NAS expression plasmid was introduced during cotransformation, resulting in successful production of rNCL in the culture medium. Moreover, to obtain a higher production yield of rNCL, the active form of hacA cDNA encoding a transcription factor that induces an unfolded protein response was cloned and expressed constitutively. This resulted in a 1.5-fold increase in the level of rNCL production (2.0 mg/liter). rNCL was purified by chromatography, and its NAS was found to be N-glycosylated as expected. The original sweetness and taste-modifying activity of rNCL were comparable to those of native NCL when confirmed by calcium imaging with human embryonic kidney cells expressing the human sweet taste receptor and by sensory tests.

Phylogenetic comparison and classification of laccase and related multicopper oxidase protein sequences

A phylogenetic analysis of more than 350 multicopper oxidases (MCOs) from fungi, insects, plants, and bacteria provided the basis for a refined classification of this enzyme family into laccases sensu stricto (basidiomycetous and ascomycetous), insect laccases, fungal pigment MCOs, fungal ferroxidases, ascorbate oxidases, plant laccase-like MCOs, and bilirubin oxidases. Within the largest group of enzymes, formed by the 125 basidiomycetous laccases, the gene phylogeny does not strictly follow the species phylogeny. The enzymes seem to group at least partially according to the lifestyle of the corresponding species. Analyses of the completely sequenced fungal genomes showed that the composition of MCOs in the different species can be very variable. Some species seem to encode only ferroxidases, whereas others have proteins which are distributed over up to four different functional clusters in the phylogenetic tree.

Studies on the microbial transformation of androst-1,4-dien-3,17-dione with Acremonium strictum

The strain of Acremonium strictum PTCC 5282 was applied to investigate the biotransformation of androst-1,4-dien-3,17-dione (I; ADD). Microbial products obtained were purified by preparative TLC and the pure metabolites were characterized on the basis of their spectroscopic features (13C NMR, 1H NMR, FTIR, MS) and physical constants (melting points and optical rotations). The 15 alpha-Hydroxyandrost-1,4-dien-3,17-dione (II), 17 beta-hydroxyandrost-1,4-dien-3-one (III), androst-4-en-3,17-dione (IV; AD), 15 alpha-hydroxyandrost-4-en-3,17-dione (V), 15 alpha,17 beta-dihydroxyandrost-1,4-dien-3-one (VI) and testosterone (VII) were produced during this fermentation. Formation of the 15 alpha,17 beta-dihydroxy derivative of ADD is reported for the first time during steroid biotransformation. The bioconversion reactions observed were 1,2-hydrogenation, 15 alpha-hydroxylation and 17-ketone reduction. From the time course profile of this biotransformation, ketone reduction and 1,2-hydrogenation were observed from the first day of fermentation while 15 alpha-hydroxylation occurred from the third day. Optimum concentration of the substrate, which gave the maximum bioconversion efficiency, was 0.5 mg ml(-1) in one batch. The highest yield of the microbial products recorded in this work was achieved within the pH range 6.5-7.3 and at the temperature of 27 degrees C.

Production, properties and application to biocatalysis of a novel extracellular alkaline phenol oxidase from the thermophilic fungus Scytalidium thermophilum

Scytalidium thermophilum produces an extracellular phenol oxidase on glucose-containing medium. Certain phenolic acids, specifically gallic acid and tannic acid, induce the expression of the enzyme. Production at 45 degrees C in batch cultures is growth-associated and is enhanced in the presence of 160 microM CuSO4 x 5 H2O and 3 mM gallic acid. The highest enzyme activity is observed at pH 7.5 and 65 degrees C, on catechol. When incubated for 1 h at pH 7 and pH 8, 95% and 86% of the activity is retained. Thermostability decreases gradually from 40 degrees C to 80 degrees C. Estimated molecular mass is c. 83 kDa, and pI is acidic at c. 5.4. Substrate specificity and inhibition analysis in culture supernatants suggest that the enzyme has unique properties showing activity towards catechol; 3,4-dihydroxy-L-phenylalanine (L-DOPA); 4-amino-N, N-diethylaniline (ADA); p-hydroquinone; gallic acid; tannic acid and caffeic acid, and no activity towards L-tyrosine, guaiacol, 2,2'-azino-bis(3-ethyl-benzthiazoline-6-sulphonic acid) (ABTS) and syringaldazine. Inhibition is observed in the presence of salicyl hydroxamic acid (SHAM) and p-coumaric acid. Enzyme activity is enhanced by cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP), and the organic solvents dimethyl sulfoxide (DMSO) and ethanol. No inhibition is observed in the presence of carbon monoxide. Benzoin, benzoyl benzoin and hydrobenzoin are converted into benzil, and stereoselective oxidation is observed on hydrobenzoin. The reported enzyme is novel due to its catalytic properties resembling mainly catechol oxidases, but displaying some features of laccases at the same time.

Production of bifunctional proteins by Aspergillus awamori: Llama variable heavy chain antibody fragment (VHH) R9 coupled to Arthromyces ramosus peroxidase (ARP)

The Arthromyces ramosus peroxidase gene (arp) was genetically fused to either the 5'- or 3'-terminal ends of the gene encoding llama variable heavy chain antibody fragment V(HH) R9, resulting in the fusion expression cassettes ARP-R9 or R9-ARP. Aspergillus awamori transformants were obtained which produced up to 30 mgl(-1) fusion protein in the culture medium. Both fusion proteins showed peroxidase activity in an ABTS activity test. Considerable amounts of fusion protein were detected intracellularly, suggesting that the fungus encounters problems in secreting these kind of proteins. ELISA experiments showed that ARP-R9 was less able to bind its antigen, the azo-dye RR6, as compared to R9-ARP. Furthermore, in contrast to R9-ARP, ARP-R9 bound to RR6 did not show peroxidase activity anymore. These results indicate that fusion of ARP to the C-terminus of the antibody fragment V(HH) R9 (R9-ARP) is the preferred orientation.

Structural close-related aromatic compounds have different effects on laccase activity and on lcc gene expression in the ligninolytic fungus Trametes sp. I-62

Nine phenolic compounds (p-coumaric acid, ferulic acid, guaiacol, syringol, p-methoxyphenol, pyrocatechol, phloroglucinol, 3,5-dihydroxybenzoic acid, and syringaldazine) were tested for their ability to increase laccase production in the ligninolytic basidiomycete Trametes sp. I-62. All these compounds resulted in increases in laccase activity, with the highest levels being detected in the presence of p-coumaric acid (273-fold) and guaiacol (73-fold). The three laccase isozyme genes in this fungus lcc1, lcc2, and lcc3 are differentially expressed in the presence of some of these aromatics with total lcc transcript levels differing markedly depending on the aromatic compound tested. Guaiacol (the best inducer of lcc gene transcription) and p-coumaric acid selectively induced expression of lcc1 and lcc2; ferulic acid induced lcc3 expression, while 3,5-dihydroxybenzoic acid had no marked effect on laccase gene transcription. The results demonstrate that close-related aromatic compounds appear to have different effects on both laccase activity levels and lcc gene expression in this basidiomycete.

Expression and production of llama variable heavy-chain antibody fragments (VHHs) by Aspergillus awamori

We report the expression and production of llama variable heavy-chain antibody fragments (V(HH)s) by Aspergillus awamori. Fragments encoding V(HH)s were cloned in a suitable Aspergillus expression vector and transformants secreting V(HH) fragments were analysed for integrated gene copy-numbers, mRNA levels and protein production. Functional V(HH)s were detected in the culture medium, indicating the feasibility of producing this type of protein in a fungal expression system. Secreted V(HH)s were subjected to (extracellular) degradation, which could be partially prevented by the addition of BSA to the culture medium.

RGS21 is a novel regulator of G protein signalling selectively expressed in subpopulations of taste bud cells

Abstract G-protein-mediated signalling processes are involved in sweet and bitter taste transduction. In particular, the G protein alpha-subunit gustducin has been implicated in these processes. One of the limiting factors for the time-course of cellular responses induced by tastants is therefore the intrinsic GTPase activity of alpha-gustducin, which determines the lifetime of the active G protein complex. In several signalling systems specific 'regulator of G protein signalling' (RGS) proteins accelerate the GTPase activity of G protein alpha-subunits. Using differential screening approaches, we have identified a novel RGS protein termed RGS21, which represents the smallest known member of this protein family. Reverse transcription polymerase chain reaction and in situ hybridization experiments demonstrated that RGS21 is expressed selectively in taste tissue where it is found in a subpopulation of sensory cells. Furthermore, it is coexpressed in individual taste cells with bitter and sweet transduction components including alpha-gustducin, phospholipase Cbeta2, T1R2/T1R3 sweet taste receptors and T2R bitter taste receptors. In vitro binding assays demonstrate that RGS21 binds alpha-gustducin in a conformation-dependent manner and has the potential to interact with the same Galpha subtypes as T1R receptors. These results suggest that RGS21 could play a regulatory role in bitter as well as sweet taste transduction processes.

Efficient production of Arthromyces ramosus peroxidase by Aspergillus awamori

The heterologous production of Arthromyces ramosus peroxidase (ARP) was analysed in the filamentous fungus Aspergillus awamori under control of the inducible endoxylanase promoter. Secretion of active ARP was achieved up to 800 mg l(-1) in shake flask cultures. Western blot analysis showed that an rARP product of the correct molecular weight was produced. In contrast to several other studies about heterologous production of heme containing peroxidases, our results suggest that in A. awamori no heme limitation exists during overproduction of ARP.

Identification of a new laccase gene and confirmation of genomic predictions by cDNA sequences of Trametes sp. I-62 laccase family

The strain Trametes sp. I-62 (CECT 20197) is a white-rot fungus with great potential for biotechnological applications in the fields of industrial waste water decolorization and clean up. Three laccase genes: lcc1, lcc2 and lcc3 have been cloned and sequenced from this basidiomycete. In this work, the coding regions of the corresponding cDNAs have been synthesized, cloned, and sequenced. They are 1563, 1563 and 1575 bp in length, respectively. Former putative intron/exon structures from genomic DNA are fully confirmed by match analysis with our cDNA sequences. Using Polymerase Chain Reaction--Restriction Fragment Length Polymorphism (PCR-RFLP) analysis, an additional laccase cDNA was also identified, corresponding to a new gene, lcc1A, which displayed 99.6% identity with lcc1 at protein level. Such high similarity between lcc1 and lcc1A sequences, and the comparison with reports from other basidiomycete laccases, suggest that in this strain these two genes are allelic variants.