Biocatalytic Production of Aldehydes: Exploring the Potential of Lathyrus cicera Amine Oxidase.

Aldehydes are a class of carbonyl compounds widely used as intermediates in the pharmaceutical, cosmetic and food industries. To date, there are few fully enzymatic methods for synthesizing these highly reactive chemicals. In the present work, we explore the biocatalytic potential of an amino oxidase extracted from the etiolated shoots of Lathyrus cicera for the synthesis of value-added aldehydes, starting from the corresponding primary amines. In this frame, we have developed a completely chromatography-free purification protocol based on crossflow ultrafiltration, which makes the production of this enzyme easily scalable. Furthermore, we determined the kinetic parameters of the amine oxidase toward 20 differently substituted aliphatic and aromatic primary amines, and we developed a biocatalytic process for their conversion into the corresponding aldehydes. The reaction occurs in aqueous media at neutral pH in the presence of catalase, which removes the hydrogen peroxide produced during the reaction itself, contributing to the recycling of oxygen. A high conversion (>95%) was achieved within 3 h for all the tested compounds.

Novel approach using activated cellulose film for efficient immobilization of purified diamine oxidase to enhance enzyme performance and stability.

The presence of various contaminants in foodstuffs has led to serious public health concerns. Diamine oxidase (DAO) has attracted tremendous attention for guarding food safety as well as clinical and environmental industries. In this study, DAO from Pisum sativum (Pea) seedlings was extracted and purified by dialysis and gel filtration. Purified DAO was covalently immobilized onto the surface of nitrocellulose membrane using glutaraldehyde. The obtained bioaffinity support has efficiently shown high yield immobilization of DAO from pea seedlings. The optimal conditions of free and immobilized DAO activity were evaluated against the substrate, Putrescine dihydrochloride. The influence of pH, temperature, storage stability, and reusability of immobilized enzyme with comparison to the free enzyme was studied and the results showed that the stabilities were significantly enhanced compared with free counterpart. Residual activity of the immobilized enzyme was 59% of the initial activity after being recycled 10 times. We approve that this novel low cost immobilized DAO carrier presents a new approach in large scale applications.

Amine oxidase from Euphorbia characias: Kinetic and structural characterization.

This minireview focuses on a plant copper/2,4,5-trihydroxyphenyl alanine quinone amine oxidase isolated from the latex of the shrub Euphorbia characias (ELAO). This enzyme has been investigated in terms of both molecular structure and kinetic mechanism. The characterization of this enzyme allowed us to identify specific amino acids and domains that play a key role in modulating substrate access into the active site not only for ELAO but also for other plant and mammalian amine oxidases. As mammalian amine oxidases are implicated in several physiological and pathological conditions, the deep structural characterization of their active site accession mechanisms could be the starting point for the development of enzyme modulators with high therapeutic potential. Thus, this paper gives structural/functional insights that open new perspectives in the research about the whole amine oxidase family.

Expression and functional analysis of the lysine decarboxylase and copper amine oxidase genes from the endophytic fungus Colletotrichum gloeosporioides ES026.

Huperzine A (HupA) isolated from Huperzia serrata is an important compound used to treat Alzheimer's disease (AD). Recently, HupA was reported in various endophytic fungi, with Colletotrichum gloeosporioides ES026 previously isolated from H. serrata shown to produce HupA. In this study, we performed next-generation sequencing and de novo RNA sequencing of C. gloeosporioides ES026 to elucidate the molecular functions, biological processes, and biochemical pathways of these unique sequences. Gene ontology and Kyoto Encyclopedia of Genes and Genomes assignments allowed annotation of lysine decarboxylase (LDC) and copper amine oxidase (CAO) for their conversion of L-lysine to 5-aminopentanal during HupA biosynthesis. Additionally, we constructed a stable, high-yielding HupA-expression system resulting from the overexpression of CgLDC and CgCAO from the HupA-producing endophytic fungus C. gloeosporioides ES026 in Escherichia coli. Quantitative reverse transcription polymerase chain reaction analysis confirmed CgLDC and CgCAO expression, and quantitative determination of HupA levels was assessed by liquid chromatography high-resolution mass spectrometry, which revealed that elevated expression of CgLDC and CgCAO produced higher yields of HupA than those derived from C. gloeosporioides ES026. These results revealed CgLDC and CgCAO involvement in HupA biosynthesis and their key role in regulating HupA content in C. gloeosporioides ES026.

Molecular cloning, expression, and functional analysis of the copper amine oxidase gene in the endophytic fungus Shiraia sp. Slf14 from Huperzia serrata.

Huperzine A (HupA) is a drug used for the treatment of Alzheimer's disease. However, the biosynthesis of this medicinally important compound is not well understood. The HupA biosynthetic pathway is thought to be initiated by the decarboxylation of lysine to form cadaverine, which is then converted to 5-aminopentanal by copper amine oxidase (CAO). In this study, we cloned and expressed an SsCAO gene from a HupA-producing endophytic fungus, Shiraia sp. Slf14. Analysis of the deduced protein amino acid sequence showed that it contained the Asp catalytic base, conserved motif Asn-Tyr-Asp/Glu, and three copper-binding histidines. The cDNA of SsCAO was amplified and expressed in Escherichia coli BL21(DE3), from which a 76 kDa protein was obtained. The activity of this enzyme was tested, which provided more information about the SsCAO gene in the endophytic fungus. Gas Chromatograph-Mass Spectrometry (GC-MS) revealed that this SsCAO could accept cadaverine as a substrate to produce 5-aminopentanal, the precursor of HupA. Phylogenetic tree analysis indicated that the SsCAO from Shiraia sp. Slf14 was closely related to Stemphylium lycopersici CAO. This is the first report on the cloning and expression of a CAO gene from HupA-producing endophytic fungi. Functional characterization of this enzyme provides new insights into the biosynthesis of the HupA an anti-Alzheimer's drug.

Characterization of recombinant human diamine oxidase (rhDAO) produced in Chinese Hamster Ovary (CHO) cells.

Human diamine oxidase (hDAO) efficiently degrades polyamines and histamine. Reduced enzyme activities might cause complications during pregnancy and be involved in histamine intolerance. So far hDAO has been characterized after isolation from either native sources or the heterologous production in insect cells. Accessibility to human enzyme is limited and insect cells produce non-human glycosylation patterns that may alter its biochemical properties. We present the heterologous expression of hDAO in Chinese Hamster Ovary (CHO) cells and a three step purification protocol. Analysis of metal content using ICP-MS revealed that 93% of the active sites were occupied by copper. Topaquinone (TPQ) cofactor content was determined using phenylhydrazine titration. Ninety-four percent of DAO molecules contained TPQ and therefore the copper content at the active site was indirectly confirmed. Mass spectrometric analysis was conducted to verify sequence integrity of the protein and to assess the glycosylation profile. Electronic circular dichroism and UV-vis spectra data were used to characterize structural properties. The substrate preference and kinetic parameters were in accordance with previous publications. The establishment of a recombinant production system for hDAO enables us to generate decent amounts of protein with negligible impurities to address new scientific questions.

Syncephalastrum racemosum amine oxidase with high catalytic efficiency toward ethanolamine and its application in ethanolamine determination.

Our screening study yielded a copper amine oxidase (SrAOX) from Syncephalastrum racemosum, which showed much higher affinity and catalytic efficiency toward ethanolamine (EA) than any other amine oxidase (AOX). Following purification of the enzyme to electrophoretic homogeneity from a cell-free extract, the maximum activity toward EA was detected at pH 7.2-7.5 and 45 °C. The SrAOX complementary DNA (cDNA) was composed of a 2052-bp open reading frame encoding a 683-amino acid protein with a molecular mass of 77,162 Da. The enzyme functions as a homodimer. The deduced amino acid sequence of SrAOX showed 55.3 % identity to Rhizopus delemar AOX and contains two consensus sequences of Cu-AOX, NYDY, and HHQH, suggesting SrAOX is a type 1 Cu-AOX (i.e., a topaquinone enzyme). Structural homology modeling showed that residues (112)ML(113), (141)FADTWG(146) M158, and N318 are unique, and T144 possibly characterizes the substrate specificity of SrAOX. The recombinant enzyme (rSrAOX) was produced using Escherichia coli. Steady-state kinetic analysis of rSrAOX activity toward EA (pH 7.5 and 45 °C) gave K m and k cat values of 0.848 ± 0.009 mM and 9.11 ± 0.13 s(-1), respectively. The standard curves were linear between 0.1 and 2 mM EA, and 10 µg mL(-1)-2.5 mg mL(-1) (15 µM-3.6 mM) phosphatidylethanolamine using Streptomyces chromofuscus phospholipase D, respectively, was sufficiently sensitive for clinical use.

Characterization of two amine oxidases from Aspergillus carbonarius AIU 205.

We have reported that Aspergillus carbonarius AIU 205, which was isolated by our group, produced three enzymes exhibiting oxidase activity for 4-aminobutanamide (4-ABAD) (J. Biosci. Bioeng., 117, 263-268, 2014). Among three enzymes, characteristics of enzyme I have been revealed, but those of the other two enzymes have not. In this study, we purified enzymes II and III, and compared their characteristics with those of enzyme I. Enzymes II and III also oxidized aliphatic monoamines, aromatic amines, and aliphatic aminoalcohols. In addition, the oxidase activity of both enzymes was strongly inhibited by carbonyl reagents and specific inhibitors for copper-containing amine oxidases. Thus, enzymes II and III were also classified into the copper-containing amine oxidase group (EC 1.4.3.6) along with enzyme I. However, these three enzymes differed from each other in their enzymatic, kinetic, and physicochemical properties. The N-terminal amino acid sequences also differed from each other; that of enzyme I was modified, that of enzyme II was similar to those of peroxisomal copper-containing amine oxidases, and that of enzyme III was similar to those of copper-containing amine oxidases from the genus Aspergillus. Therefore, we concluded that A. carbonarius AIU 205 produced three different types of amine oxidase in the mycelia.

The plant histaminase: a promising enzyme with antioxidant properties versus histamine release in isoprenaline-induced myocardial infarction in rats.

The present study was designed to evaluate possible protective effects of purified histaminase from Lathyrus sativus L. seedling on the myocardial injuries upon isoprenaline-induced myocardial infarction in rats. In this regard, blood histamine concentration, creatine kinase-MB (CK-MB) activity, antioxidant status, and histopathological changes of the hearts were measured. A total of 40 adult male Sprague-Dawley rats were divided into five equal groups and treated in the following order: control (normal saline), isoprenaline (isoproterenol 110 mg/kg BW), Isopren.-H1 (isoprenaline plus histaminase 80 U/kg BW), Isopren.-H2 (isoprenaline plus histaminase 120 U/kg BW), and Isopren.-H3 (isoprenaline plus histaminase 160 U/kg BW). Myocardial infarction was manifested by a significant elevation in the level of CK-MB and histopathological findings in isoprenaline group when compared to controls. In contrast, histaminase pretreatment at dose of 160 U/kg prevented isoprenaline-induced histamine release and significantly decreased CK-MB activity as well as histopathological changes in Isopren.-H3 group. A significant increase in the catalase (CAT) and superoxide dismutase (SOD) activities was also observed by histaminase treatment in Isopren.-H2 and Isopren.-H3 groups. Although the activity of glutathione peroxidase (GPx) increased significantly to suppress oxidative stress in isoprenaline group, it was not able to prevent lipid peroxidation (as shown by TBARS concentration) in the heart of rats. In conclusion, the plant-originated histaminase presented as a promising enzyme with antioxidant properties against histamine release and myocardial infarction in rats, and it seems be a suitable therapeutic agent for future clinical trials in humans.

Bioconversion of airborne methylamine by immobilized recombinant amine oxidase from the thermotolerant yeast Hansenula polymorpha.

Aliphatic amines, including methylamine, are air-pollutants, due to their intensive use in industry and the natural degradation of proteins, amino acids, and other nitrogen-containing compounds in biological samples. It is necessary to develop systems for removal of methylamine from the air, since airborne methylamine has a negative effect on human health. The primary amine oxidase (primary amine : oxygen oxidoreductase (deaminating) or amine oxidase, AMO; EC 1.4.3.21), a copper-containing enzyme from the thermotolerant yeast Hansenula polymorpha which was overexpressed in baker's yeast Saccharomyces cerevisiae, was tested for its ability to oxidize airborne methylamine. A continuous fluidized bed bioreactor (CFBR) was designed to enable bioconversion of airborne methylamine by AMO immobilized in calcium alginate (CA) beads. The results demonstrated that the bioreactor with immobilized AMO eliminates nearly 97% of the airborne methylamine. However, the enzymatic activity of AMO causes formation of formaldehyde. A two-step bioconversion process was therefore proposed. In the first step, airborne methylamine was fed into a CFBR which contained immobilized AMO. In the second step, the gas flow was passed through another CFBR, with alcohol oxidase from the yeast H. polymorpha immobilized in CA, in order to decompose the formaldehyde formed in the first step. The proposed system provided almost total elimination of the airborne methylamine and the formaldehyde.

Characterization and application of aminoamide-oxidizing enzyme from Aspergillus carbonarius AIU 205.

We isolated Aspergillus carbonarius AIU 205 as a new producer of an enzyme catalyzing oxidative deamination of 4-aminobutanamide (4-ABAD) to 4-oxobutanamide with the subsequent release of ammonia and hydrogen peroxide. Since the strain produced three enzymes with different Km values for 4-ABAD, the enzyme with lowest Km value (0.31 mM) was purified and revealed certain remarkable properties. The enzyme also oxidized aliphatic monoamines, aromatic amines and aliphatic aminoalcohols, but did not oxidize l-amino acids and aliphatic diamines. The Vmax/Km values for aliphatic monoamines were higher than that for 4-ABAD, and the enzyme activity was strongly inhibited by inhibitors of copper-containing amine oxidases. Thus, it was concluded that the enzyme might belong to a group of copper-containing amine oxidase. The 4-ABAD oxidase activity of this enzyme was optimum at pH 7.0, and the enzyme activity at pH 6.0 was 65% of that at pH 7.0. The enzyme was useful for increasing the sensitivity of l-lysine assay using l-amino acid oxidase/monooxygenase from Pseudomonas sp. AIU 813.

Identification of stage-specific breast markers using quantitative proteomics.

Matched healthy and diseased tissues from breast cancer patients were analyzed by quantitative proteomics. By comparing proteomic profiles of fibroadenoma (benign tumors, three patients), DCIS (noninvasive cancer, three patients), and invasive ductal carcinoma (four patients), we identified protein alterations that correlated with breast cancer progression. Three 8-plex iTRAQ experiments generated an average of 826 protein identifications, of which 402 were common. After excluding those originating from blood, 59 proteins were significantly changed in tumor compared with normal tissues, with the majority associated with invasive carcinomas. Bioinformatics analysis identified relationships between proteins in this subset including roles in redox regulation, lipid transport, protein folding, and proteasomal degradation, with a substantial number increased in expression due to Myc oncogene activation. Three target proteins, cofilin-1 and p23 (increased in invasive carcinoma) and membrane copper amine oxidase 3 (decreased in invasive carcinoma), were subjected to further validation. All three were observed in phenotype-specific breast cancer cell lines, normal (nontransformed) breast cell lines, and primary breast epithelial cells by Western blotting, but only cofilin-1 and p23 were detected by multiple reaction monitoring mass spectrometry analysis. All three proteins were detected by both analytical approaches in matched tissue biopsies emulating the response observed with proteomics analysis. Tissue microarray analysis (361 patients) indicated cofilin-1 staining positively correlating with tumor grade and p23 staining with ER positive status; both therefore merit further investigation as potential biomarkers.

Characterization of amine oxidases from Arthrobacter aurescens and application for determination of biogenic amines.

Biogenic amines (BAs) that are produced through naturally occurring decarboxylation of amino acids have toxicological effects on humans. Bacterial amine oxidases are useful tools for the rapid quantification of BAs in foods. To develop amine oxidases for the rapid detection of BAs, the genes for amine oxidases from Arthobacter aurescens TC-1, designated AMAO1, AMAO2, and AMAO3, respectively, were cloned and expressed in Escherichia coli. AMAO1 was catalytically inactive to BAs, and AMAO3 showed a narrow substrate spectrum. In contrast, AMAO2 exhibited activity with relative k cat/K M values of 100:49.6:7.6 for 2-phenylethylamine, tyramine, and histamine, respectively. AMAO2 also utilized putrescine and spermidine as substrates, with four or five orders of magnitude lower k cat/K M values than that of 2-phenylethylamine. AMAO2 and AMAO3 were seriously affected by substrate inhibition. Using BA mixtures (consisting of 2-phenylethylamine, tyramine, and histamine) as samples, the detection range of the enzymatic analysis of BA using AMAO2 was determined to be 2.5-120 µM, and its detection limit was 2.3 µM. Analysis of five commercial cheese products revealed that the BA contents determined by the enzymatic methods showed a good agreement with the sum of three monoamines and histamine by HPLC. Therefore, the enzymatic assay using AMAO2 can be used in quality control of food products through rapid, sensitive, and preliminary estimation of major BAs including the most important TyrN and HisN in foods.

Purification of diamine oxidase and its properties in germinated fava bean (Vicia faba L.).

BACKGROUND: γ-Aminobutyric acid (GABA) is a non-protein amino acid with bioactive functions for human health. Diamine oxidase (DAO, EC 1.4.3.6) is one of the key enzymes for GABA formation. In the present study, this enzyme was purified from 5 day germinated fava bean and its properties were investigated in vitro. RESULTS: The molecular mass of the enzyme estimated by Sephadex G-100 gel filtration was 121 kDa. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) displayed a single band at a molecular mass of 52 kDa. The enzyme had optimal activity at 40 °C and retained its activity after being incubated at 30 °C for 30 min. It showed higher activity at pH 6.5 than at other pH values. The enzyme was significantly inhibited by Mg(2+), Cu(2+), Fe(3+), aminoguanidine, ethylene glycol tetraacetic acid (EGTA), ethylene diamine tetraacetic acid disodium salt (EDTA-Na(2)), L-cysteine and ß-mercaptoethanol. The K(m) value of DAO was 0.23 mmol L(-1) for putrescine and 0.96 mmol L(-1) for spermidine. However, the enzyme did not degrade spermine. CONCLUSION: DAO from germinated fava bean was purified. The optimal reaction temperature and pH of the enzyme were mild. The enzyme had higher affinity to putrescine than to spermidine and spermine.

Implication for functions of the ectopic adipocyte copper amine oxidase (AOC3) from purified enzyme and cell-based kinetic studies.

AOC3 is highly expressed in adipocytes and smooth muscle cells, but its function in these cells is currently unknown. The in vivo substrate(s) of AOC3 is/are also unknown, but could provide an invaluable clue to the enzyme's function. Expression of untagged, soluble human AOC3 in insect cells provides a relatively simple means of obtaining pure enzyme. Characterization of enzyme indicates a 6% titer for the active site 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor and corrected k(cat) values as high as 7 s(-1). Substrate kinetic profiling shows that the enzyme accepts a variety of primary amines with different chemical features, including nonphysiological branched-chain and aliphatic amines, with measured k(cat)/K(m) values between 10(2) and 10(4) M(-1) s(-1). K(m)(O(2)) approximates the partial pressure of oxygen found in the interstitial space. Comparison of the properties of purified murine to human enzyme indicates k(cat)/K(m) values that are within 3 to 4-fold, with the exception of methylamine and aminoacetone that are ca. 10-fold more active with human AOC3. With drug development efforts investigating AOC3 as an anti-inflammatory target, these studies suggest that caution is called for when screening the efficacy of inhibitors designed against human enzymes in non-transgenic mouse models. Differentiated murine 3T3-L1 adipocytes show a uniform distribution of AOC3 on the cell surface and whole cell K(m) values that are reasonably close to values measured using purified enzymes. The latter studies support a relevance of the kinetic parameters measured with isolated AOC3 variants to adipocyte function. From our studies, a number of possible substrates with relatively high k(cat)/K(m) have been discovered, including dopamine and cysteamine, which may implicate a role for adipocyte AOC3 in insulin-signaling and fatty acid metabolism, respectively. Finally, the demonstrated AOC3 turnover of primary amines that are non-native to human tissue suggests possible roles for the adipocyte enzyme in subcutaneous bacterial infiltration and obesity.

Structure and activity of Aspergillus nidulans copper amine oxidase.

Aspergillus nidulans amine oxidase (ANAO) has the unusual ability among the family of copper and trihydroxyphenylalanine quinone-containing amine oxidases of being able to oxidize the amine side chains of lysine residues in large peptides and proteins. We show here that in common with the related enzyme from the yeast Pichia pastoris, ANAO can promote the cross-linking of tropoelastin and oxidize the lysine residues in α-casein proteins and tropoelastin. The crystal structure of ANAO, the first for a fungal enzyme in this family, has been determined to a resolution of 2.4 Å. The enzyme is a dimer with the archetypal fold of a copper-containing amine oxidase. The active site is the most open of any of those of the structurally characterized enzymes in the family and provides a ready explanation for its lysine oxidase-like activity.

Zymographic assay of plant diamine oxidase on entrapped peroxidase polyacrylamide gel electrophoresis. A study of stability to proteolysis.

A zymographic assay of diamine oxidase (DAO, histaminase, EC 1.4.3.6), based on a coupled peroxidase reaction, and its behavior at proteolysis in simulated gastric and intestinal conditions, are described. The DAO activity from a vegetal extract of Lathyrus sativus seedlings was directly determined on sodium dodecyl sulfate polyacrylamide electrophoretic gels containing entrapped horseradish peroxidase, with putrescine as substrate of histaminase and ortho-phenylenediamine as co-substrate of peroxidase. The accumulation of azo-aniline, as peroxidase-catalyzed oxidation product, led to well-defined yellow-brown bands on gels, with intensities corresponding to the enzymatic activity of DAO. After image analysis of gels, a linear dependency of DAO content (Coomassie-stained protein bands) and of its enzymatic activity (zymographic bands) with the concentration of the vegetal extract was obtained. In simulated gastric conditions (pH 1.2, 37 degrees C), the DAO from the vegetal extract lost its enzymatic activity before 15 min of incubation, either in the presence or absence of pepsin. The protein pattern (Coomassie-stained) revealed that the DAO content from the vegetal extract was kept almost constant in the simulated intestinal fluid (containing pancreatin or not), with a slight diminution in the presence of pancreatic proteases. After 10 h of incubation at 37 degrees C, the DAO enzymatic activity from the vegetal extract was 44.7% in media without pancreatin and 13.6% in the presence of pancreatin, whereas the purified DAO retained only 4.65% of its initial enzymatic activity in the presence of pancreatin.

Novel copper amine oxidase activity from rat liver mitochondria matrix.

Copper containing amine oxidases (Cu-AO) represent a heterogeneous class of enzymes classified as EC 1.4.3.6. The present study reports preliminary results on the presence of a novel amine oxidase activity in rat liver mitochondria lysates. Such enzymatic activity was found in the soluble mitochondrial fraction, obtained by simple osmotic shock. The mitochondrial amine oxidase was isolated by affinity chromatography on a newly synthesised spermine-Sepharose. SDS-PAGE showed a single band at about 60kDa. Upon chromatographic purification, the enzymatic activity was very labile. The crude enzyme activity was tested by spectrophotometric measurements, determining hydrogen peroxide production following oxidative deamination of different substrates, such as polyamines (spermine, spermidine, putrescine and cadaverine) and monoamines (dopamine and benzylamine). The activity, observed on polyamines and not on monoamines, was inhibited by semicarbazide and azide, but not by pargyline, clorgyline and l-deprenil. Enzyme specificity was tested on several diamines characterized by different carbon atom chain length in the range 2-6 carbon atoms. The highest activity was found with 1,2-diamino-ethane and the highest affinity with 1,5-diamino-pentane. The above reported results suggest the presence of a novel copper-dependent amine oxidase in liver mitochondria matrix.

Structure of a xenon derivative of Escherichia coli copper amine oxidase: confirmation of the proposed oxygen-entry pathway.

The mechanism of molecular oxygen entry into the buried active site of the copper amine oxidase family has been investigated in several family members using biochemical, structural and in silico methods. These studies have revealed a structurally conserved beta-sandwich which acts as a hydrophobic reservoir from which molecular oxygen can take several species-specific preferred pathways to the active site. Escherichia coli copper amine oxidase (ECAO) possesses an extra N-terminal domain that lies close to one entrance to the beta-sandwich. In order to investigate whether the presence of this domain alters molecular oxygen entry in this enzyme, xenon was used as a molecular oxygen binding-site probe. The resulting 2.5 A resolution X-ray crystal structure reveals xenon bound in similar positions to those observed in xenon-derivative crystal structures of other family members, suggesting that the N-terminal domain does not affect oxygen entry and that the E. coli enzyme takes up oxygen in a similar manner to the rest of the copper amine oxidase family.

Enzymatic characterization of an amine oxidase from Arthrobacter sp. used to measure phosphatidylethanolamine.

Ethanolamine oxidase was screened with the aim of using it to establish a novel enzymatic phosphatidylethanolamine assay. Ethanolamine oxidase activity was detected in the crude extract of Arthrobacter sp., and the enzyme was purified more than 15-fold in three steps with a 54% yield. SDS-PAGE revealed the presence of only one band, which migrated, with an apparent molecular mass of 70 kDa. Biochemical characterization of the enzyme showed phenylethylamine to be the preferred substrate, with the highest kcat/Km value. The primary structure, determined by sequencing the cloned gene, showed a high degree of identity to Cu-containing phenylethylamine oxidase (64%). When heterologously overexpressed in Escherichia coli, the enzyme exhibited only a trace of amine oxidase activity, but high levels of activity emerged after exposure to Cu2+, as is typical of recombinant copper amine oxidases. Preliminary application of this enzyme coupled with phospholipase D for determination of phosphatidylethanolamine is also described. This is the first enzymatic method for the measurement of phosphatidylethanolamine.