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Solmi L, Rosli HG, Pombo MA, Stalder S, Rossi FR, Romero FM, Ruiz OA, Gárriz A. Inferring the Significance of the Polyamine Metabolism in the Phytopathogenic Bacteria Pseudomonas syringae: A Meta-Analysis Approach. Front Microbiol 2022; 13:893626. [PMID: 35602047 PMCID: PMC9120772 DOI: 10.3389/fmicb.2022.893626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 04/13/2022] [Indexed: 11/21/2022] Open
Abstract
To succeed in plant invasion, phytopathogenic bacteria rely on virulence mechanisms to subvert plant immunity and create favorable conditions for growth. This process requires a precise regulation in the production of important proteins and metabolites. Among them, the family of compounds known as polyamines have attracted considerable attention as they are involved in important cellular processes, but it is not known yet how phytopathogenic bacteria regulate polyamine homeostasis in the plant environment. In the present study, we performed a meta-analysis of publicly available transcriptomic data from experiments conducted on bacteria to begin delving into this topic and better understand the regulation of polyamine metabolism and its links to pathogenicity. We focused our research on Pseudomonas syringae, an important phytopathogen that causes disease in many economically valuable plant species. Our analysis discovered that polyamine synthesis, as well as general gene expression activation and energy production are induced in the early stages of the disease. On the contrary, synthesis of these compounds is inhibited whereas its transport is upregulated later in the process, which correlates with the induction of virulence genes and the metabolism of nitrogen and carboxylic acids. We also found that activation of plant defense mechanisms affects bacterial polyamine synthesis to some extent, which could reduce bacterial cell fitness in the plant environment. Furthermore, data suggest that a proper bacterial response to oxidative conditions requires a decrease in polyamine production. The implications of these findings are discussed.
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Affiliation(s)
- Leandro Solmi
- Laboratorio de Estrés Biótico y Abiótico en Plantas-Instituto Tecnológico de Chascomús (INTECh), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de General San Martín (CONICET-UNSAM), Chascomús, Argentina
| | - Hernán G. Rosli
- Laboratorio de Interacciones Planta Patógeno-Instituto de Fisiología Vegetal (INFIVE), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de La Plata (CONICET-UNLP), La Plata, Argentina
| | - Marina A. Pombo
- Laboratorio de Interacciones Planta Patógeno-Instituto de Fisiología Vegetal (INFIVE), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de La Plata (CONICET-UNLP), La Plata, Argentina
| | - Santiago Stalder
- Laboratorio de Estrés Biótico y Abiótico en Plantas-Instituto Tecnológico de Chascomús (INTECh), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de General San Martín (CONICET-UNSAM), Chascomús, Argentina
| | - Franco R. Rossi
- Laboratorio de Estrés Biótico y Abiótico en Plantas-Instituto Tecnológico de Chascomús (INTECh), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de General San Martín (CONICET-UNSAM), Chascomús, Argentina
| | - Fernando M. Romero
- Laboratorio de Estrés Biótico y Abiótico en Plantas-Instituto Tecnológico de Chascomús (INTECh), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de General San Martín (CONICET-UNSAM), Chascomús, Argentina
| | - Oscar A. Ruiz
- Laboratorio de Estrés Biótico y Abiótico en Plantas-Instituto Tecnológico de Chascomús (INTECh), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de General San Martín (CONICET-UNSAM), Chascomús, Argentina
| | - Andrés Gárriz
- Laboratorio de Estrés Biótico y Abiótico en Plantas-Instituto Tecnológico de Chascomús (INTECh), Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de General San Martín (CONICET-UNSAM), Chascomús, Argentina
- *Correspondence: Andrés Gárriz,
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2
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Che S, Liang Y, Chen Y, Wu W, Liu R, Zhang Q, Bartlam M. Structure of Pseudomonas aeruginosa spermidine dehydrogenase: a polyamine oxidase with a novel heme-binding fold. FEBS J 2022; 289:1911-1928. [PMID: 34741591 DOI: 10.1111/febs.16264] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 10/31/2021] [Accepted: 11/04/2021] [Indexed: 11/29/2022]
Abstract
The opportunistic pathogen Pseudomonas aeruginosa can utilize polyamines (including putrescine, cadaverine, 4-aminobutyrate, spermidine, and spermine) as its sole source of carbon and nitrogen. Spermidine dehydrogenase (SpdH) is a component of one of the two polyamine utilization pathways identified in P. aeruginosa, but little is known about its structure and function. Here, we report the first crystal structure of SpdH from P. aeruginosa to 1.85 Å resolution. The resulting core structure confirms that SpdH belongs to the polyamine oxidase (PAO) family with flavin-binding and substrate-binding domains. A unique N-terminal extension wraps around the flavin-binding domain of SpdH and is required for heme binding, placing a heme cofactor in close proximity to the FAD cofactor. Structural and mutational analysis reveals that residues in the putative active site at the re side of the FAD isoalloxazine ring form part of the catalytic machinery. PaSpdH features an unusual active site and lacks the conserved lysine that forms part of a lysine-water-flavin N5 atom interaction in other PAO enzymes characterized to date. Mutational analysis further confirms that heme is required for catalytic activity. This work provides an important starting point for understanding the role of SpdH, which occurs universally in P. aeruginosa strains, in polyamine metabolism.
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Affiliation(s)
- Shiyou Che
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
| | - Yakun Liang
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
| | - Yujing Chen
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
| | - Wenyue Wu
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
| | - Ruihua Liu
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
| | - Qionglin Zhang
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
| | - Mark Bartlam
- State Key Laboratory of Medicinal Chemical Biology, Nankai International Advanced Research Institute (Shenzhen Futian), College of Life Sciences, Nankai University, Tianjin, China
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3
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Abstract
Polyamine oxidases (PAOs) are characterized by a broad variability in catalytic properties and subcellular localization, and impact key cellular processes in diverse organisms. In the present study, a comprehensive phylogenetic analysis was performed to understand the evolution of PAOs across the three domains of life and particularly within eukaryotes. Phylogenetic trees show that PAO-like sequences of bacteria, archaea, and eukaryotes form three distinct clades, with the exception of a few procaryotes that probably acquired a PAO gene through horizontal transfer from a eukaryotic donor. Results strongly support a common origin for archaeal PAO-like proteins and eukaryotic PAOs, as well as a shared origin between PAOs and monoamine oxidases. Within eukaryotes, four main lineages were identified that likely originated from an ancestral eukaryotic PAO before the split of the main superphyla, followed by specific gene losses in each superphylum. Plant PAOs show the highest diversity within eukaryotes and belong to three distinct clades that underwent to multiple events of gene duplication and gene loss. Peptide deletion along the evolution of plant PAOs of Clade I accounted for further diversification of function and subcellular localization. This study provides a reference for future structure-function studies and emphasizes the importance of extending comparisons among PAO subfamilies across multiple eukaryotic superphyla.
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Affiliation(s)
- Daniele Salvi
- Department of Health, Life and Environmental Sciences, University of L'Aquila, 67100, L'Aquila, Italy
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Characterization of Quinohemoprotein Amine Dehydrogenase from Pseudomonas putida. Biosci Biotechnol Biochem 2016; 62:469-78. [PMID: 27315927 DOI: 10.1271/bbb.62.469] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Quinohemoprotein amine dehydrogenase (AMDH) was purified and crystallized from the soluble fraction of Pseudomonas putida IFO 15366 grown on n-butylamine medium. AMDH gave a single component in analytical ultracentrifugation showing an intrinsic sedimentation coefficient of 5.8s. AMDH showed a typical absorption spectrum of cytochrome c showing maxima at 554, 522, 420, and 320 nm in the reduced form and one peak at 410 nm, a shoulder at 350 nm, and a broad hill around 530 nm in the oxidized form. The oxidized enzyme was specifically reduced by the addition of amine substrate. AMDH was composed of three different subunits, 60, 40, and 20 kDa, with the total molecular weight of 120,000. Two moles of heme c were detected per mole of AMDH and the 60-kDa subunit was found to be the heme c-carrying subunit. By redox-cycling quinone staining, a positive reaction band corresponding to the 20-kDa subunit was detected after developed by SDS-PAGE, but the 20 kDa band was scarcely stained by conventional protein staining. Only a silver staining method was possible to detect the subunit after the protein was developed by SDS-PAGE. p-Nitrophenylhydrazine-inhibited AMDH was dissociated into subunits and the 20-kDa subunit showed an absorption maximum at 455 nm, indicating Schiff base formation between the carbonyl cofactor in AMDH and the carbonyl reagent. Thus, AMDH is different from nonheme quinoprotein methylamine dehydrogenase and aromatic amine dehydrogenase in many respects. The presence of an azurin-like blue protein was identified and purified from the same cell-free extract of P. putida as AMDH was purified. The blue protein was reduced specifically during AMDH reaction, suggesting that the blue protein is the direct electron acceptor in amine oxidation. The amine oxidation system was reconstituted successfully only by AMDH, the blue protein, and the cytoplasmic membranes of the organism. The function of the 40-kDa subunit is unknown at the moment. The properties of AMDH were compared with other bacterial amine dehydrogenases so far reported.
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Kim SH, Wang Y, Khomutov M, Khomutov A, Fuqua C, Michael AJ. The Essential Role of Spermidine in Growth of Agrobacterium tumefaciens Is Determined by the 1,3-Diaminopropane Moiety. ACS Chem Biol 2016; 11:491-9. [PMID: 26682642 DOI: 10.1021/acschembio.5b00893] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ubiquitous polyamine spermidine is indispensable for eukaryotic growth and cell proliferation. A conserved vital function of spermidine across eukaryotes is conferred by its aminobutyl group that is transferred to a single lysine in translation factor eIF5A to form the essential hypusine post-translational modification required for cellular translation. In direct contrast, although spermidine is absolutely essential for growth of α-proteobacterial plant pathogen Agrobacterium tumefaciens, we have found, by employing a suite of natural polyamines and synthetic methylated spermidine analogues together with spermidine biosynthetic mutants, that it is solely the 1,3-diaminopropane moiety of spermidine that is required for growth. Indeed, any polyamine containing an intact terminal 1,3-diaminopropane moiety can replace spermidine for growth, including the simple diamine 1,3-diaminopropane itself, a paradigm shift in understanding polyamine function in bacteria. We have identified for the first time a spermidine retroconversion activity in bacteria, producing diamine putrescine from triamine spermidine; however, exogenously supplied tetraamine spermine is resistant to retroconversion. When spermidine levels are pharmacologically decreased, synthesis of spermine from spermidine is induced via the same biosynthetic enzymes, carboxyspermidine dehydrogenase and carboxyspermidine decarboxylase that produce spermidine from putrescine, the first identification of a spermine biosynthetic pathway in bacteria. This also suggests that spermidine represses spermine biosynthesis, but when spermidine levels decrease, it is then converted by carboxyspermidine dehydrogenase and decarboxylase enzymes to spermine, which is resistant to retroconversion and constitutes a sequestered pool of protected 1,3-diaminopropane modules required for growth. We also identify an efficient N-acetylspermidine deacetylase activity, indicative of a sophisticated bacterial polyamine homeostasis system.
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Affiliation(s)
- Sok Ho Kim
- Department
of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Yi Wang
- Department
of Biology, Indiana University, Bloomington, Indiana 47405, United States
| | - Maxim Khomutov
- Engelhardt
Institute of Molecular Biology, Russian Academy of Sciences, Vavilov Street 32, Moscow 119991, Russia
| | - Alexey Khomutov
- Engelhardt
Institute of Molecular Biology, Russian Academy of Sciences, Vavilov Street 32, Moscow 119991, Russia
| | - Clay Fuqua
- Department
of Biology, Indiana University, Bloomington, Indiana 47405, United States
| | - Anthony J. Michael
- Department
of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
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Green R, Hanfrey CC, Elliott KA, McCloskey DE, Wang X, Kanugula S, Pegg AE, Michael AJ. Independent evolutionary origins of functional polyamine biosynthetic enzyme fusions catalysing de novo diamine to triamine formation. Mol Microbiol 2011; 81:1109-24. [PMID: 21762220 DOI: 10.1111/j.1365-2958.2011.07757.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We have identified gene fusions of polyamine biosynthetic enzymes S-adenosylmethionine decarboxylase (AdoMetDC, speD) and aminopropyltransferase (speE) orthologues in diverse bacterial phyla. Both domains are functionally active and we demonstrate the novel de novo synthesis of the triamine spermidine from the diamine putrescine by fusion enzymes from β-proteobacterium Delftia acidovorans and δ-proteobacterium Syntrophus aciditrophicus, in a ΔspeDE gene deletion strain of Salmonella enterica sv. Typhimurium. Fusion proteins from marine α-proteobacterium Candidatus Pelagibacter ubique, actinobacterium Nocardia farcinica, chlorobi species Chloroherpeton thalassium, and β-proteobacterium D. acidovorans each produce a different profile of non-native polyamines including sym-norspermidine when expressed in Escherichia coli. The different aminopropyltransferase activities together with phylogenetic analysis confirm independent evolutionary origins for some fusions. Comparative genomic analysis strongly indicates that gene fusions arose by merger of adjacent open reading frames. Independent fusion events, and horizontal and vertical gene transfer contributed to the scattered phyletic distribution of the gene fusions. Surprisingly, expression of fusion genes in E. coli and S. Typhimurium revealed novel latent spermidine catabolic activity producing non-native 1,3-diaminopropane in these species. We have also identified fusions of polyamine biosynthetic enzymes agmatine deiminase and N-carbamoylputrescine amidohydrolase in archaea, and of S-adenosylmethionine decarboxylase and ornithine decarboxylase in the single-celled green alga Micromonas.
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Affiliation(s)
- Robert Green
- Institute of Food Research, Norwich Research Park, Colney, Norwich NR47UA, UK
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7
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Dasu VV, Nakada Y, Ohnishi-Kameyama M, Kimura K, Itoh Y. Characterization and a role of Pseudomonas aeruginosa spermidine dehydrogenase in polyamine catabolism. Microbiology (Reading) 2006; 152:2265-2272. [PMID: 16849793 DOI: 10.1099/mic.0.28920-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosaPAO1 has two possible catabolic pathways of spermidine and spermine; one includes thespuAandspuBproducts with unknown functions and the other involves spermidine dehydrogenase (SpdH; EC 1.5.99.6) encoded by an unknown gene. The properties of SpdH inP. aeruginosaPAO1 were characterized and the correspondingspdHgene in this strain identified. The deduced SpdH (620 residues, calculatedMrof 68 861) had a signal sequence of 28 amino acids at the amino terminal and a potential transmembrane segment between residues 76 and 92, in accordance with membrane location of the enzyme. Purified SpdH oxidatively cleaved spermidine into 1,3-diaminopropane and 4-aminobutyraldehyde with a specific activity of 37 units (mg protein)−1and aKmvalue of 36 μM. The enzyme also hydrolysed spermine into spermidine and 3-aminopropanaldehyde with a specific activity of 25 units (mg protein)−1and aKmof 18 μM. Knockout ofspdHhad no apparent effect on the utilization of both polyamines, suggesting that this gene is minimally involved in polyamine catabolism. However, whenspdHwas fused to the polyamine-inducible promoter ofspuA, it fully restored the ability of aspuAmutant to utilize spermidine. It is concluded that SpdH can perform a catabolic rolein vivo, butP. aeruginosaPAO1 does not produce sufficient amounts of the enzyme to execute this function.
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Affiliation(s)
- Veeranki Venkata Dasu
- National Food Research Institute, Kannondai 2-1-12, Tsukuba, Ibaraki 305-8642, Japan
| | - Yuji Nakada
- National Food Research Institute, Kannondai 2-1-12, Tsukuba, Ibaraki 305-8642, Japan
| | | | - Keitarou Kimura
- National Food Research Institute, Kannondai 2-1-12, Tsukuba, Ibaraki 305-8642, Japan
| | - Yoshifumi Itoh
- Akita Research Institute for Food and Brewing, Sanuki 4-26, Araya-machi, Akita 010-1623, Japan
- National Food Research Institute, Kannondai 2-1-12, Tsukuba, Ibaraki 305-8642, Japan
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8
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Limburg J, Mure M, Klinman JP. Cloning and characterization of histamine dehydrogenase from Nocardioides simplex. Arch Biochem Biophys 2005; 436:8-22. [PMID: 15752704 DOI: 10.1016/j.abb.2004.11.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 11/24/2004] [Indexed: 11/16/2022]
Abstract
Histamine dehydrogenase (NSHADH) can be isolated from cultures of Nocardioides simplex grown with histamine as the sole nitrogen source. A previous report suggested that NSHADH might contain the quinone cofactor tryptophan tryptophyl quinone (TTQ). Here, the hdh gene encoding NSHADH is cloned from the genomic DNA of N. simplex, and the isolated enzyme is subjected to a full spectroscopic characterization. Protein sequence alignment shows NSHADH to be related to trimethylamine dehydrogenase (TMADH: EC 1.5.99.7), where the latter contains a bacterial ferredoxin-type [4Fe-4S] cluster and 6-S-cysteinyl FMN cofactor. NSHADH has no sequence similarity to any TTQ containing amine dehydrogenases. NSHADH contains 3.6+/-0.3 mol Fe and 3.7+/-0.2 mol acid labile S per subunit. A comparison of the UV/vis spectra of NSHADH and TMADH shows significant similarity. The EPR spectrum of histamine reduced NSHADH also supports the presence of the flavin and [4Fe-4S] cofactors. Importantly, we show that NSHADH has a narrow substrate specificity, oxidizing only histamine (K(m)=31+/-11 microM, k(cat)/K(m)=2.1 (+/-0.4)x10(5)M(-1)s(-1)), agmatine (K(m)=37+/-6 microM, k(cat)/K(m)=6.0 (+/-0.6)x10(4)M(-1)s(-1)), and putrescine (K(m)=1280+/-240 microM, k(cat)/K(m)=1500+/-200 M(-1)s(-1)). A kinetic characterization of the oxidative deamination of histamine by NSHADH is presented that includes the pH dependence of k(cat)/K(m) (histamine) and the measurement of a substrate deuterium isotope effect, (D)(k(cat)/K(m) (histamine))=7.0+/-1.8 at pH 8.5. k(cat) is also pH dependent and has a reduced substrate deuterium isotope of (D)(k(cat))=1.3+/-0.2.
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Affiliation(s)
- Julian Limburg
- Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
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Tanaka K, Matsuno E, Shimizu E, Shibai H, Yorifuji T. Purification and characterization of aminopropionaldehyde dehydrogenase from Arthrobacter sp. TMP-1. FEMS Microbiol Lett 2001; 195:191-6. [PMID: 11179651 DOI: 10.1111/j.1574-6968.2001.tb10520.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Aminopropionaldehyde dehydrogenase was purified to apparent homogeneity from 1,3-diaminopropane-grown cells of Arthrobacter sp. TMP-1. The native molecular mass and the subunit molecular mass of the enzyme were approximately 20,5000 and 52,000, respectively, suggesting that the enzyme is a tetramer of identical subunits. The apparent Michaelis constant (K(m)) for 1,3-diaminopropane was approximately 3 microM. The enzyme equally used both NAD(+) and NADP(+) as coenzymes. The apparent K(m) values for NAD(+) and NADP(+) were 255 microM and 108 microM, respectively. The maximum reaction rates (V(max)) for NAD(+) and NADP(+) were 102 and 83.3 micromol min(-1) mg(-1), respectively. Some tested aliphatic aldehydes and aromatic aldehydes were inert as substrates. The optimum pH was 8.0-8.5. The enzyme was sensitive to sulfhydryl group-modifying reagents.
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Affiliation(s)
- K Tanaka
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Shinshu University, 8304 Minamiminowa, Nagano 399-4598, Japan.
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Tao Y, Chen KY. Purification of deoxyhypusine synthase from Neurospora crassa to homogeneity by substrate elution affinity chromatography. J Biol Chem 1995; 270:383-6. [PMID: 7814398 DOI: 10.1074/jbc.270.1.383] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Deoxyhypusine synthase is an NAD(+)-dependent enzyme that catalyzes the formation of deoxyhypusine residue on the eIF-5A precursor by using spermidine as the substrate. Deoxyhypusine synthase bound tightly to 1,12-diaminododecane-agarose and could be eluted selectively by spermidine. This finding enabled us to develop a simple two-column procedure to purify deoxyhypusine synthase from Neurospora crassa to apparent homogeneity. The purified enzyme had a specific activity of 130,000 units/mg of protein, representing a 64,000-fold purification from cell extracts. Size exclusion chromatography indicated that the native enzyme had a molecular mass of 180 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the pure enzyme showed a single band at the 40-kDa position, suggesting that Neurospora deoxyhypusine synthase is a homotetramer. Deoxyhypusine synthase appeared to be hydrophobic and required non-ionic detergent such as Tween 20 to stabilize the activity. Treatment of the enzyme with sulfhydryl reagents resulted in a complete loss of activity. Inclusion of NAD+ reduced the inactivation rate by manyfold, indicating the presence of -SH groups at or near the active site. Partial amino acid sequences of four peptide fragments that cover about one quarter of the enzyme were obtained for cDNA and genomic cloning work.
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Affiliation(s)
- Y Tao
- Department of Chemistry, Rutgers, State University of New Jersey, Piscataway 08855-0939
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