Enzymatic Characterization of an Amine Oxidase from Arthrobacter Sp
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80365 (381) Biosci. Biotechnol. Biochem., 72, 80365-1–7, 2008 Enzymatic Characterization of an Amine Oxidase from Arthrobacter sp. Used to Measure Phosphatidylethanolamine Hiroko OTA,1;* Hideto TAMEZANE,2;* Yoshie SASANO,2 Eisaku HOKAZONO,2 y Yuko YASUDA,1 Shin-ichi SAKASEGAWA,1; Shigeyuki IMAMURA,1 Tomohiro TAMURA,3;4 and Susumu OSAWA2 1Asahi Kasei Pharma Corporation, Shizuoka 410-4321, Japan 2Kyushu University, Division of Biological Science and Technology, Department of Health Science, School of Medicine, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan 3Research Institute of Genome-Based Biofactory, National Institute of Advanced Industrial Sciences and Technology (AIST), 2-17-2-1 Tsukisamu-Higashi, Toyohira-ku, Sapporo 062-8517, Japan 4Laboratory of Molecular Environmental Microbiology, Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan Received May 29, 2008; Accepted July 1, 2008; Online Publication, October 7, 2008 [doi:10.1271/bbb.80365]Advance View Ethanolamine oxidase was screened with the aim of most abundant membrane phospholipid in mammals, using it to establish a novel enzymatic phosphatidyle- accounting for 20% to 50% of total phospholipids. thanolamine assay. Ethanolamine oxidase activity was Together with phosphatidylserine, the most abundant detected in the crude extract of Arthrobacter sp., and the phospholipid in mammalian membranes, PE plays key enzyme was purified more than 15-fold in three steps roles in a variety of biological processes, including with a 54% yield. SDS–PAGE revealed the presence of apoptosis and cell signaling.1) The conventional methods only one band, which migrated, with an apparent for assaying PE are thin-layer chromatography2) and Proofs3) molecular mass of 70 kDa. Biochemical characterization HPLC-based analysis, but, these methods are too time of the enzyme showed phenylethylamine to be the consuming to be used in routine work. In the present preferred substrate, with the highest kcat/Km value. study, therefore, our aim was to begin to develop a The primary structure, determined by sequencing the convenient new PE assay that can be used routinely to cloned gene, showed a high degree of identity to Cu- analyze PE levels in, for example, serum and plasma. containing phenylethylamine oxidase (64%). When Our strategy for this assay was to employ a contin- heterologously overexpressed in Escherichia coli, the uously coupled reaction consisting of three independent enzyme exhibited only a trace of amine oxidase activity, enzymatic reactions: (i) hydrolysis of the phosphodiester but high levels of activity emerged after exposure to bond of PE using phospholipase D (EC 3.1.4.4) Cu2þ, as is typical of recombinant copper amine to generate phosphatidic acid and ethanolamine,4) (ii) oxidases. Preliminary application of this enzyme cou- oxidative deamination of the ethanolamine with con- pled with phospholipase D for determination of phos- comitant reduction of O2 to generate glycolaldehyde, phatidylethanolamine is also described. This is the first NH3, and H2O2, and (iii) an oxidative coupling reaction enzymatic method for the measurement of phosphati- with 4-aminoantipyrine and, perhaps, phenol catalyzed dylethanolamine. by peroxidase (EC 1.11.1.7) in the presence of H2O2. In this scheme, an enzyme that can oxidize ethanol- Key words: copper amine oxidase; Arthrobacter sp.; amine is required, and the object of the present study phosphatidylethanolamine was to express and purify an ethanolamine oxidative enzyme. Phosphatidylethanolamine (PE) is an aminophospho- Two classes of phylogenetically unrelated enzymes lipid found in biological membranes. It is the second are known to catalyze the oxidation of monoamines with * These authors contributed equally to this work. y To whom correspondence should be addressed. Fax: +81-558-76-7149; E-mail: [email protected] Abbreviations: PE, phosphatidylethanolamine; TPQ, 2,4,5-trihydroxyphenylalanine quinone; AAO, Arthrobacter sp. copper amine oxidase; LB, Luria-Bertani; TOOS, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-m-toluidine; AGAO, Arthrobacter globiformis phenylethylamine oxidase 80365-2 H. OTA et al. broad substrate specificity. These enzymes are flavin After the cell debris was removed by centrifugation containing amine oxidoreductase (Pfam PF01593, EC (15;000 g for 60 min), the supernatant was collected as 1.4.3.4), and copper amine oxidase (PF01179, EC the crude extract. Thereafter, solid (NH4)2SO4 was 1.4.3.6). The reactions catalyzed by these two enzymes added to a concentration of 18% (w/v), and the resulting are formally identical, and the products are correspond- mixture was centrifuged at 10;000 g for 15 min to pellet- ing aldehydes, NH3, and H2O2. Copper amine oxidases out protein. Again the supernatant was collected, and are dimers comprised of identical 70–90 kDa subunits, this time solid (NH4)2SO4 was added, to a concentration each of which contains a single copper ion and a of 12%, after which the mixture was centrifuged at covalently bound cofactor formed through post-transla- 10;000 g for 15 min to precipitate the AAO. The tional modification of a tyrosine side chain to 2,4,5- precipitated AAO was dissolved in the standard buffer trihydroxyphenylalanine quinone (TPQ).5,6) Copper and dialyzed against 50 volumes of the same buffer. The amine oxidase has been purified from a wide variety dialyzate, containing the enzyme, was loaded onto 2 of organisms and characterized,7) and the crystal struc- liters of DEAE-Sepharose Fast Flow gel packed in a tures of the enzymes from Arthrobacter globiformis8) BPG100 column (10 cm column i.d., GE Healthcare, and Escherichia coli9) have been solved. Tokyo) equilibrated with the buffer. After the column We detected ethanolamine oxidase activity in a cell- was washed with the same buffer, the enzyme was free crude extract of Arthrobacter sp., and the purified eluted with a linear gradient of 0–0.5 M NaCl. The enzyme was found to be a copper amine oxidase (AAO). fractions containing the enzyme were dialyzed against Here we describe this enzyme’s biochemical character- 20 volumes of the standard buffer, and the enzyme ization and its heterologous overexpression in E. coli.In solution was loaded onto 0.5 liters of Q-Sepharose High addition, preliminary application of this enzyme coupled Performance gel packed in a XK50 column (5 cm with phospholipase D for determination of PE is also column i.d., GE Healthcare) equilibrated with the same described.Advance Viewbuffer. After the column was washed with the buffer, the bound enzyme was eluted with a linear gradient of Materials and Methods 0–0.5 M KCl. The resulting enzyme solution was con- centrated using a 30-kDa centrifugal filter device Microorganism and growth conditions. Arthrobacter (Millipore, Bedford, MA), and dialyzed against 100 sp. (FERM P-06240, BP-0421), originally isolated from volumes of buffer. soil, was used as the source of AAO and its chromo- somal DNA. The cells were grown in a medium Analyses of N-terminal and inner amino acid se- containing 1.0% yeast extract, 1.0% meat extract, quences. Once purified, the enzyme was denatured using 1.0% peptone, 1.0% corn steep liquor, and 0.05% 1 M urea and then digested with Lys-C or Asp-N Proofs phenylethylamine at pH 7.5. The bacterium was aerobi- endopeptidase (Roche) for 17 h at 37 C. The digested cally cultivated for 40 h at 30 C. fragments were then purified on a reverse-phase Capcell Pak C18 HPLC column (Shiseido, Tokyo) using a Enzyme assay and protein measurement. Unless solvent system composed of a 50-min linear gradient of otherwise specified, the standard reaction mixture con- 10% to 70% acetonitrile containing 0.1% trifluoroacetic tained 20 mM potassium phosphate (pH 7.5), 0.1 mM acid. The flow rate was 0.5 ml/min, and the eluate was tyramine, 0.03% 4-aminoantipyrine, 0.02% N,N-Bis(4- monitored at an absorbance of 215 nm. The overall sulfobutyl)-3-methylaniline (Dojin, Kumamoto, Japan), amino acid sequences of these peptide fragments and the and 5 U/ml peroxidase (Sigma, St. Louis, MO) in a total N-terminal region of the purified AAO were analyzed volume of 1.0 ml. The reaction was started by the by automated Edman degradation using an Applied addition of 15 ml of enzyme solution. The reaction Biosystems gas-phase protein sequencer. mixture was incubated at 37 C in a cuvette, and the increase in absorbance at 546 nm was followed spec- Cloning and sequencing of the AAO gene. A 500-bp À1 trophotometrically (d ¼ 1 cm and "546 ¼ 16 mM fragment of the AAO gene was amplified using cmÀ1). One U of enzyme was defined as the amount oligonucleotide primers corresponding to the double- catalyzing the oxidation of 1 mmole of tyramine per min underlined inner peptides shown in Fig. 2 (sense, 50-ggn at pH 7.5 at 37 C. Protein was measured using a Bio- gcn ccn tty cay car cay ytn tty gg-30, and antisense, 50- Rad protein assay kit (Bio-Rad, Hercules, CA); bovine acn cay tty ccn mgn acn gar gay gay cc-30). Chromo- serum albumin served as the standard protein. somal DNA isolated from Arthrobacter sp. as described previously10) served as the template. For genome Purification of amine oxidase from Arthrobacter sp. walking to clone the missing part of the AAO gene, an All operations were carried out at room temperature, and LA PCR in vitro Cloning Kit (Takara, Shiga, Japan) was 10 mM potassium phosphate buffer (pH 7.0) was used as used as instructed by the manufacturer.11) The entire the standard buffer throughout purification. Arthrobacter AAO gene was then amplified using oligonucleotide sp. cells were lysed in buffer containing 0.5% lysozyme, primers 50-ttt aca tgt ctg aaa cca ccg ccg tca ata-30 1mM EDTA, and 0.05% Triton X-100 for 1 h at 38 C.