RESUMO
Shimwellia blattae is an enteric bacterium and produces endogenous enzymes that convert 1,2-propanediol (1,2-PD) to 1-propanol, which is expected to be used as a fuel substitute and a precursor of polypropylene. Therefore, if S. blattae could be induced to generate its own 1,2-PD from sugars, it might be possible to produce 1-propanol from sugars with this microorganism. Here, two 1,2-PD production pathways were constructed in S. blattae, resulting in two methods for 1-propanol production with the bacterium. One method employed the L-rhamnose utilization pathway, in which L-rhamnose is split into dihydroxyacetone phosphate and 1,2-PD. When wild-type S. blattae was cultured with L-rhamnose, an accumulation of 1,2-PD was observed. The other method for producing 1,2-PD was to introduce an engineered 1,2-PD production pathway from glucose into S. blattae. In both cases, the produced 1,2-PD was then converted to 1-propanol by 1,2-PD converting enzymes, whose production was induced by the addition of glycerol.
Assuntos
1-Propanol/metabolismo , Enterobacteriaceae/metabolismo , Glucose/metabolismo , Engenharia Metabólica , Ramnose/metabolismo , Biotransformação , Meios de Cultura/química , Enterobacteriaceae/crescimento & desenvolvimento , Fermentação , Glicerol/metabolismo , Propilenoglicol/metabolismoRESUMO
L-allo-Threonine aldolase (LATA), a pyridoxal-5'-phosphate-dependent enzyme from Aeromonas jandaei DK-39, stereospecifically catalyzes the reversible interconversion of L-allo-threonine to glycine and acetaldehyde. Here, the crystal structures of LATA and its mutant LATA_H128Y/S292R were determined at 2.59 and 2.50â Å resolution, respectively. Their structures implied that conformational changes in the loop consisting of residues Ala123-Pro131, where His128 moved 4.2â Å outwards from the active site on mutation to a tyrosine residue, regulate the substrate specificity for L-allo-threonine versus L-threonine. Saturation mutagenesis of His128 led to diverse stereoselectivity towards L-allo-threonine and L-threonine. Moreover, the H128Y mutant showed the highest activity towards the two substrates, with an 8.4-fold increase towards L-threonine and a 2.0-fold increase towards L-allo-threonine compared with the wild-type enzyme. The crystal structures of LATA and its mutant LATA_H128Y/S292R reported here will provide further insights into the regulation of the stereoselectivity of threonine aldolases targeted for the catalysis of L-allo-threonine/L-threonine synthesis.
Assuntos
Aeromonas/enzimologia , Glicina Hidroximetiltransferase/metabolismo , Mutação , Sequência de Bases , Domínio Catalítico , Primers do DNA , Glicina Hidroximetiltransferase/química , Glicina Hidroximetiltransferase/genética , Modelos Moleculares , Reação em Cadeia da Polimerase , Conformação Proteica , Especificidade por SubstratoRESUMO
(R)-3-Quinuclidinol, a useful compound for the synthesis of various pharmaceuticals, can be enantioselectively produced from 3-quinuclidinone by 3-quinuclidinone reductase. Recently, a novel NADH-dependent 3-quinuclidionone reductase (AtQR) was isolated from Agrobacterium tumefaciens, and showed much higher substrate-binding affinity (>100 fold) than the reported 3-quinuclidionone reductase (RrQR) from Rhodotorula rubra. Here, we report the crystal structure of AtQR at 1.72 Å. Three NADH-bound protomers and one NADH-free protomer form a tetrameric structure in an asymmetric unit of crystals. NADH not only acts as a proton donor, but also contributes to the stability of the α7 helix. This helix is a unique and functionally significant part of AtQR and is related to form a deep catalytic cavity. AtQR has all three catalytic residues of the short-chain dehydrogenases/reductases family and the hydrophobic wall for the enantioselective reduction of 3-quinuclidinone as well as RrQR. An additional residue on the α7 helix, Glu197, exists near the active site of AtQR. This acidic residue is considered to form a direct interaction with the amine part of 3-quinuclidinone, which contributes to substrate orientation and enhancement of substrate-binding affinity. Mutational analyses also support that Glu197 is an indispensable residue for the activity.
Assuntos
Agrobacterium tumefaciens/enzimologia , Oxirredutases/química , Oxirredutases/metabolismo , Quinuclidinas/metabolismo , Agrobacterium tumefaciens/química , Agrobacterium tumefaciens/metabolismo , Sítios de Ligação , Cristalografia por Raios X , Modelos Moleculares , NAD/metabolismo , Conformação Proteica , Estereoisomerismo , Especificidade por SubstratoRESUMO
Conjugated polyketone reductase C2 (CPR-C2) from Candida parapsilosis IFO 0708, identified as a nicotinamide adenine dinucleotide phosphate (NADPH)-dependent ketopantoyl lactone reductase, belongs to the aldo-keto reductase superfamily. This enzyme reduces ketopantoyl lactone to D-pantoyl lactone in a strictly stereospecific manner. To elucidate the structural basis of the substrate specificity, we determined the crystal structures of the apo CPR-C2 and CPR-C2/NADPH complex at 1.70 and 1.80 Å resolutions, respectively. CPR-C2 adopted a triose-phosphate isomerase barrel fold at the core of the structure. Binding with the cofactor NADPH induced conformational changes in which Thr27 and Lys28 moved 15 and 5.0 Å, respectively, in the close vicinity of the adenosine 2'-phosphate group of NADPH to form hydrogen bonds. Based on the comparison of the CPR-C2/NADPH structure with 3-α-hydroxysteroid dehydrogenase and mutation analyses, we constructed substrate binding models with ketopantoyl lactone, which provided insight into the substrate specificity by the cofactor-induced structure. The results will be useful for the rational design of CPR-C2 mutants targeted for use in the industrial manufacture of ketopantoyl lactone.
Assuntos
Oxirredutases do Álcool/química , Oxirredutases do Álcool/metabolismo , Candida/enzimologia , NADP/química , NADP/metabolismo , 4-Butirolactona/análogos & derivados , 4-Butirolactona/metabolismo , Cristalografia por Raios X , Análise Mutacional de DNA , Modelos Moleculares , Ligação Proteica , Conformação ProteicaRESUMO
The L-pantoyl lactone (L-PL) dehydrogenase (LPLDH) gene (lpldh) has been cloned from Rhodococcus erythropolis AKU2103, and addition of 1,2-propanediol (1,2-PD) was shown to be required for lpldh expression in this strain. In this study, based on an exploration of the nucleotide sequence around lpldh, a TetR-like regulator gene, which we designated lplR, was found upstream of lpldh, and three putative open reading frames existed between the two genes. Disruption of lplR led to 22.8 times higher lpldh expression, even without 1,2-PD induction, than that in wild-type R. erythropolis AKU2103 without 1,2-PD addition. Introduction of a multicopy vector carrying lplR (multi-lplR) into the wild-type and ΔlplR strains led to no detectable LPLDH activity even in the presence of 1,2-PD. The results of an electrophoretic mobility shift assay revealed that purified LplR bound to a 6-bp inverted-repeat sequence located in the promoter/operator region of the operon containing lpldh. These results indicated that LplR is a negative regulator in lpldh expression. Based on the clarification of the expression mechanism of lpldh, recombinant cells showing high LPLDH activity were constructed and used as a catalyst for the conversion of L-PL to ketopantoyl lactone. Finally, a promising production process of D-PL from DL-PL was constructed.
Assuntos
Oxirredutases do Álcool/biossíntese , Regulação Bacteriana da Expressão Gênica , Proteínas Repressoras/metabolismo , Rhodococcus/enzimologia , Rhodococcus/genética , 4-Butirolactona/análogos & derivados , 4-Butirolactona/metabolismo , Clonagem Molecular , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Bacteriano/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Dosagem de Genes , Técnicas de Inativação de Genes , Teste de Complementação Genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Regiões Promotoras Genéticas , Propilenoglicol/metabolismo , Ligação Proteica , Proteínas Repressoras/genética , Análise de Sequência de DNARESUMO
Ketopantoic acid (KPA) reductase catalyzes the stereospecific reduction of ketopantoic acid to D-pantoic acid. Based on the N-terminal amino acid sequence of KPA reductase from Stenotrophomonas maltophilia 845, the KPA reductase gene was cloned from S. maltophilia NBRC14161 and sequenced. This gene contains an open reading frame of 777 bp encoding 258 amino acid residues, and the deduced amino acid sequence showed high similarity to the SDR superfamily proteins. An expression vector, pETSmKPR, containing the full KPA reductase gene was constructed and introduced into Escherichia coli BL21 (DE3) to overexpress the enzyme. Bioreduction of KPA using E. coli transformant cells coexpressing KPA reductase together with cofactor regeneration enzyme gene was also performed. The conversion yield of KPA to D-pantoic acid reached over 88% with a substrate concentration up to 1.17 M.
Assuntos
Oxirredutases do Álcool/genética , Oxirredutases do Álcool/metabolismo , Escherichia coli/metabolismo , Hidroxibutiratos/metabolismo , Cetoácidos/metabolismo , Stenotrophomonas maltophilia/enzimologia , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Escherichia coli/genética , Expressão Gênica , Dados de Sequência Molecular , Fases de Leitura Aberta , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Stenotrophomonas maltophilia/genéticaRESUMO
The 1,2-propanediol (1,2-PD) inducible membrane-bound L-pantoyl lactone (L-PL) dehydrogenase (LPLDH) has been isolated from Rhodococcus erythropolis AKU2103 (Kataoka et al. in Eur J Biochem 204:799, 1992). Based on the N-terminal amino acid sequence of LPLDH and the highly conserved amino acid sequence in homology search results, the LPLDH gene (lpldh) was cloned. The gene consists of 1,179 bases and encodes a protein of 392 amino acid residues. The deduced amino acid sequence showed high similarity to the proteins of the FMN-dependent α-hydroxy acid dehydrogenase/oxidase family. The overexpression vector pKLPLDH containing lpldh with its upstream region (1,940 bp) was constructed and introduced into R. erythropolis AKU2103. The recombinant R. erythropolis AKU2103 harboring pKLPLDH showed six times higher LPLDH activity than the wild-type strain. Conversion of L-PL to ketopantoyl lactone was achieved with 92% or 80% conversion yield when the substrate concentration was 0.768 or 1.15 M, respectively. Stereoinversion of L-PL to D-PL was also carried out by using the combination of recombinant R. erythropolis AKU2103 harboring pKLPLDH and ketopantoic acid-reducing Escherichia coli.
Assuntos
4-Butirolactona/análogos & derivados , Oxirredutases do Álcool/genética , Oxirredutases do Álcool/metabolismo , Rhodococcus/enzimologia , 4-Butirolactona/metabolismo , Clonagem Molecular , DNA Bacteriano/química , DNA Bacteriano/genética , Expressão Gênica , Dados de Sequência Molecular , Oxirredução , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Análise de Sequência de DNA , Análise de Sequência de Proteína , Homologia de Sequência de AminoácidosRESUMO
NADP(+)-dependent aminoalcohol dehydrogenase (AADH) of Rhodococcus erythropolis MAK154 catalyzes the reduction of (S)-1-phenyl-1-keto-2-methylaminopropane ((S)-MAK) to d-pseudoephedrine, which is used as a pharmaceutical. AADH is suggested to participate in aminoalcohol or aminoketone metabolism in this organism because it is induced by the addition of several aminoalcohols, such as 1-amino-2-propanol. Genetic analysis of around the aadh gene showed that some open reading frames (ORFs) are involved in this metabolic pathway. Four of these ORFs might form a carboxysome-like polyhedral organelle, and others are predicted to encode aminotransferase, aldehyde dehydrogenase, phosphotransferase, and regulator protein. OrfE, a homologous ORF of the FadR subfamily of GntR transcriptional regulators, lies downstream from aadh. To investigate whether or not orfE plays a role in the regulation of aadh expression, the gene disruption mutant of R. erythropolis MAK154 was constructed. The ΔorfE strain showed higher AADH activity than wild-type strain. In addition, a transformed strain, which harbored multi-orfE, showed no AADH activity even in the induced condition with 1-amino-2-propanol. These results suggest that OrfE is a negative regulator that represses aadh expression in the absence of 1-amino-2-propanol.
Assuntos
Álcool Desidrogenase/biossíntese , Regulação Bacteriana da Expressão Gênica , Pseudoefedrina/metabolismo , Proteínas Repressoras/metabolismo , Rhodococcus/enzimologia , Rhodococcus/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Deleção de Genes , Redes e Vias Metabólicas/genética , Dados de Sequência Molecular , Família Multigênica , Fases de Leitura Aberta , Proteínas Repressoras/genética , Análise de Sequência de DNARESUMO
Fermentative production of 1-propanol, which is one of the promising precursors of polypropylene production, from d-glucose, l-rhamnose and glycerol using metabolically engineered Escherichia coli was examined. To confer the ability to produce 1-propanol from 1,2-propanediol (1,2-PD) in recombinant E. coli, a part of the pdu regulon including the diol dehydratase and the propanol dehydrogenase genes together with the adenosylcobalamin (AdoCbl) regeneration enzyme genes of Klebsiella pneumoniae was cloned, and an expression vector for these genes (pRSF_pduCDEGHOQS) was constructed. Recombinant E. coli harboring pRSF_pduCDEGHOQS with 1,2-PD synthetic pathway (pKK_mde) genes, which was constructed in our previous report (Urano et al., Appl. Microbiol. Biotechnol., 99, 2001-2008, 2015), produced 16.1 mM of 1-propanol from d-glucose with a molar yield of 0.36 mol/mol after 72 h cultivation. 29.9 mM of 1-propanol was formed from l-rhamnose with a molar yield of 0.81 mol/mol using E. coli carrying only pRSF_pduCDEGHOQS. In addition, 1-propanol production from glycerol was achieved by addition of the ATP-dependent dihydroxyacetone kinase gene to E. coli harboring pKK_mde and pRSF_pduCDEGOQS. In all cases, 1-propanol production was achieved by adding only a small amount of AdoCbl.
Assuntos
1-Propanol/metabolismo , Escherichia coli/metabolismo , Fermentação , Glucose/metabolismo , Glicerol/metabolismo , Engenharia Metabólica , Ramnose/metabolismo , Cobamidas/biossíntese , Cobamidas/metabolismo , Cobamidas/farmacologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Fermentação/efeitos dos fármacos , Genes Bacterianos , Klebsiella pneumoniae/enzimologia , Klebsiella pneumoniae/genética , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Propanodiol Desidratase/genética , Propanodiol Desidratase/metabolismo , Propilenoglicóis/metabolismoRESUMO
Chiral molecule (R)-3-quinuclidinol, a valuable compound for the production of various pharmaceuticals, is efficiently synthesized from 3-quinuclidinone by using NADPH-dependent 3-quinuclidinone reductase (RrQR) from Rhodotorula rubra. Here, we report the crystal structure of RrQR and the structure-based mutational analysis. The enzyme forms a tetramer, in which the core of each protomer exhibits the α/ß Rossmann fold and contains one molecule of NADPH, whereas the characteristic substructures of a small lobe and a variable loop are localized around the substrate-binding site. Modeling and mutation analyses of the catalytic site indicated that the hydrophobicity of two residues, I167 and F212, determines the substrate-binding orientation as well as the substrate-binding affinity. Our results revealed that the characteristic substrate-binding pocket composed of hydrophobic amino acid residues ensures substrate docking for the stereospecific reaction of RrQR in spite of its loose interaction with the substrate.
RESUMO
We have cloned a gene encoding an aldehyde oxidase (ALOD) oxidized glyoxal but not glyoxylic acid from Pseudomonas sp. AIU 362. The ALOD gene contained an open reading frame consisting of 888 nucleotides corresponding to 295 amino acid residues. The deduced amino acid sequence exhibited a high similarity to those of 3-hydroxyisobutyrate dehydrogenases (3-HIBDHs). We expressed the cloned gene as an active product in Escherichia coli BL21 cells. The productivity (total units per culture broth volume) of the recombinant ALOD expressed in E. coli BL21 was 20,000-fold higher than that of ALOD in Pseudomonas sp. AIU 362. The recombinant ALOD exhibited ALOD activity and 3-HIBDH activity. The 3-HIBDH from Pseudomonas putida KT2440 also exhibited ALOD activity. Thus, the ALOD from Pseudomonas sp. AIU 362 and 3-HIBDH from P. putida KT2440 were classified into the same enzyme group.
Assuntos
Aldeído Oxidase/genética , Aldeído Oxidase/metabolismo , Pseudomonas/enzimologia , Pseudomonas/genética , Oxirredutases do Álcool/metabolismo , Aldeído Oxidase/química , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Escherichia coli/genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Pseudomonas putida/enzimologia , Pseudomonas putida/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade por SubstratoRESUMO
The aminoalcohol dehydrogenase (AADH) of Rhodococcus erythropolis MAK154, which can be used as a catalyst for the stereoselective reduction of (S)-1-phenyl-1-keto-2-methylaminopropane to d-pseudoephedrine (dPE), is inhibited by the accumulation of dPE in the reaction mixture, limiting the yield of dPE. To improve this weak point of the enzyme, random mutations were introduced into aadh, and a mutant enzyme library was constructed. The mutant library was screened with a color detectable high-throughput screening method to obtain the evolved enzymes showing the activity in the presence of a high concentration of dPE. Two mutant enzymes showed higher tolerability to dPE than the wild type enzyme. Each of these enzymes had a single amino acid substitution in a different position (G73S and S214R), and a third mutant enzyme carrying both of these amino acid substitutions was constructed. Escherichia coli transformant cells, which express mutant AADHs, showed activity in the presence of 100mg/ml dPE. A kinetic parameter analysis of the wild type and mutant enzymes was carried out. As compared with the wild type enzyme, the mutant enzymes carrying the S214R amino acid substitution or both the S214R and G73S substitutions showed higher k(cat) values, and the mutant enzymes carrying the G73S amino acid substitution or both the G73S and S214R substitutions showed higher K(m) values. These results suggest that the Ser214 residue plays an important role in enzyme activity, and that the Gly73 residue participates in enzyme-substrate binding.
Assuntos
Oxirredutases do Álcool/genética , Amino Álcoois/metabolismo , Proteínas de Bactérias/genética , Evolução Molecular Direcionada , Rhodococcus/enzimologia , Substituição de Aminoácidos , DNA Bacteriano/genética , Escherichia coli/enzimologia , Escherichia coli/genética , Mutagênese , Ligação Proteica , Rhodococcus/genética , Análise de Sequência de DNA , Especificidade por SubstratoRESUMO
We have cloned a gene encoding an alcohol oxidase (AOD) specific to aldehyde alcohols from Paenibacillus sp. AIU 311. The AOD gene contains an open reading frame consisting of 618 nucleotides corresponding to 205 amino acid residues. The deduced amino acid sequence exhibits a high similarity to that of manganese superoxide dismutases (SODs). We expressed the cloned gene as an active product in Escherichia coli BL21 cells. The productivity (total units per culture broth volume) of the recombinant AOD expressed in E. coli BL21 is 26,000-fold higher than that of AOD in Paenibacillus sp. AIU 311. The recombinant AOD also exhibits aldehyde alcohol oxidase activity and SOD activity. The recombinant cells described in this study have utility for the production of glyoxal from glycolaldehyde.