Anti-Prelog reduction of ketones by hairy root cultures

Raphanus sativus hairy roots were used in the anti-Prelog stereoselective reduction of a series of prochiral alkylaryl-ketones. Most of the bioreactions proceeded with high yields and excellent enantioselectivities. This novel biocatalyst is an easy handle system that allows the employment of the immense potential of plant enzymes in preparative asymmetric chemistry.     

山黧豆根系对H2O2诱导氧化胁迫的生理应答

以水培7d苗龄的山黧豆幼苗为材料,向水培溶液中施加不同浓度H2O2处理山黧豆幼苗24h,分析山黧豆根系受氧化胁迫的程度与抗氧化系统的应答特征,以揭示山黧豆对氧化胁迫的耐受机制。结果显示:(1)随外源H2O2处理浓度的不断增加,山黧豆幼苗侧根的数目无显著变化,而其根的鲜重则显著降低。(2)同时,根系组织的内源H2O2染色范围和程度显著增高,但根尖区域始终保持较低水平的H2O2;相反,O-·2染色范围和程度明显减少,根尖区域却始终保持较高水平的O-·2。(3)同期根系抗坏血酸(ASC)含量及过氧化氢酶(CAT)、过氧化物酶(POD)与抗坏血酸过氧化物酶(APX)的活性均表现出了先升高后降低的趋势,而超氧化物歧化酶(SOD)一直表现为持续上升的趋势。研究表明,在外源H2O2胁迫条件下,山黧豆根系O-·2的积累可能与其生长和活力呈正相关,而根系H2O2的积累则与其受氧化胁迫程度呈正相关;低浓度的H2O2处理可以提高山黧豆抗氧化系统对体内活性氧的清除能力。     

Selection of microbial biocatalysts for the reduction of cyclic and heterocyclic ketones

The reduction of carbonyl compounds plays an important role in the synthesis of complex chiral molecules. In particular, enantiopure substituted cyclic and heterocyclic compounds are useful intermediates for the synthesis of several antiviral, antitumor, and antibiotic agents, and recently, they have also been used as organocatalysts for C-C addition. Alcohol dehydrogenases (ADH) are enzymes involved in the transformation of prochiral ketones to chiral hydroxyl compounds. While significant scientific effort has been paid to the use of aliphatic and exocyclic ketones as ADH substrates, reports on (hetero)cyclic carbonyl compounds as substrates of these enzymes are scarce. In the present study, 109 bacteria and 36 fungi were screened, resulting in 10 organisms belonging to both kingdoms capable of transforming cyclic and heterocyclic ketones into the corresponding alcohols. Among them, Erwinia chrysanthemi could quantitatively reduce cyclododecanone and Geotrichum candidum could stereoselectively reduce N-Boc-3-piperidone and N-Boc-3-pyrrolidinone to their corresponding (S)-alcohols; however, the anti-Prelog isomer was obtained when acetophenone was the substrate.     

Rooting blockage in the tobacco rac mutant occurs at the initiation phase,and induces diversion to xylem differentiation

ABSTRACT

The rac mutant of Nicotiana tabacum L. cv. Xanthii is impaired in adventitious root formation. The objective of the present study was to determine whether or not the root induction phase occurs in the rac mutant, and if so, to determine what causes the induced cells to become incapable of organising root primordia. To this end, rac and wild-type shoots were cultured in vitro for 7 days under conditions suitable for obtaining roots in the wild-type (i.e., exposure to 5 µM indole-3-butyric acid for 4 h, and then transfer to hormone-free medium), and then histologically and biochemically analysed during culture. The variations in peroxidase activity, and in cellular levels of auxins and polyamines revealed that the induction phase occurs in rac shoots, although it lasts longer than in the wild-type ones. Furthermore, both auxin and polyamines were consistently higher in rac shoots compared to the wild-type. After induction, auxin and putrescine levels abruptly decreased in the wild-type shoots, whereas they decreased much more slowly in the rac mutant. The histological analysis of the wild-type shoots showed that the abrupt decrease in auxin and polyamine levels were correlated with a normal initiation phase. In fact, wild-type shoots showed cell divisions in the procambium already at day 2, resulting in the formation of root primordia at day 4, and in root emergence between days 5 and 7. In rac shoots, despite the fact that the procambium cells were activated to undergo cell division, the initiation phase was highly perturbed, and the procambial cells developed tracheary elements instead of adventitious roots. The different morphogenic responses of the two genotypes are discussed in the light of the differences in auxin content after the induction phase.     

Growth-Regulating Activity of Three 4-Hydroxycoumarin Derivatives on Inoculated Soybean Plants

Three 4-hydroxycoumarin derivatives (ethyl 2-[(4-hydroxy-2-oxo-2H-chromen-3-yl)(4-hydroxyphenyl)methyl]-3-oxobutanoate (SS-14), ethyl 2-[(4-hydroxy-2-oxo-2H-chromen-3-yl)(3-nitrophenyl)methyl]-3-oxobutanoate (SS-21), and 2-[(3,4,5-trimethoxyphenyl)(4-hydroxy-2-oxo-2H-chromen-3-yl)methyl]-3-oxobutanoate (T-2)] were tested for growth-regulating activity on nitrogen-fixing soybean plants in different concentrations: 10⁻⁵, 10⁻⁴, and 10⁻³ M. They revealed growth-regulating activity in a concentration-dependent manner. The most powerful suppression effect of T-2 on shoot and root fresh and dry biomass accumulation, length of roots, and height of plants was found. Shoot fresh biomass was suppressed in an equal extent at 10⁻³ M of the three compounds but the order of inhibition regarding the three applied concentrations was T2 > SS-14 ≈ SS-21. The compound SS-14 inhibited nodule number and nodule biomass mainly at the highest applied concentration, 10⁻³ M. The highest inhibition of nitrogenase activity was established at the three applied concentrations of the compound SS-14.     

Characterization and further stabilization of a new anti-prelog specific alcohol dehydrogenase from Thermus thermophilus HB27 for asymmetric reduction of carbonyl compounds

The use of dehydrogenases in asymmetric chemistry has exponentially grown in the last decades facilitated by the genome mining. Here, a new short-chain alcohol dehydrogenase from Thermus thermophilus HB27 has been expressed, purified, characterized and stabilized by immobilization on solid supports. The enzyme catalyzes both oxidative and reductive reactions at neutral pH with a broad range of substrates. Its highest activity was found towards the reduction of 2,2′,2″-trifluoroacetophenone (85 U/mg at 65 °C and pH 7). Moreover, the enzyme was stabilized more than 200-fold by multipoint covalent immobilization on agarose matrixes via glyoxyl chemistry. Such heterogeneous catalyst coupled to an immobilized cofactor recycling partner performed the quantitative asymmetric reduction of 2,2′,2″-trifluoroacetophenone and rac-2-phenylpropanal to (S)-(+)-α-(trifluoromethyl)benzyl alcohol and (R)-2-phenyl-1-propanol with enantiomeric excesses of 96% and 71%, respectively. To our knowledge this is the first alcohol dehydrogenase from a thermophilic source with anti-Prelog selectivity for aryl ketones and that preferentially produces R-profens.     

交替灌溉对山黧豆叶片气体交换和土壤水分以及产量指标的影响

改变土壤根系的分布以汲取深层土壤水分的能力是植物避免干旱的主要策略。山黧豆是一种抗逆性强的豆类作物,该研究通过起垄条播控制性沟灌的方式,设置传统灌溉(FI)、交替灌溉(PRD,灌水量减少50%)和不灌溉(NI)3种处理模式,探索不同灌溉模式对播种后不同时期山黧豆土壤水分、根系分布、叶片气体交换、水分利用效率和籽粒产量的影响。结果表明：(1)在FI、PRD和NI处理下,山黧豆的根系分别有89.8%、86.9%和84.9%生长在0~20 cm的表层土壤中;干旱胁迫使PRD和NI处理下深层土壤中根系的比例提高至13.05%和15.07%。(2)在整个生育期内,土壤干旱显著降低了山黧豆叶片的净光合速率、蒸腾速率和气孔导度;在种植后60 d时,PRD和NI处理下叶片的瞬时水分利用效率分别较FI处理显著提高了21.4%和14.9%。(3)干旱胁迫显著降低了山黧豆植株高度、第一豆荚高、平均结荚数和豆粒数以及地上部和根系的干重,但显著增加了根冠比;PRD处理对豆荚长度、豆荚重和每荚豆粒重没有显著影响;PRD和NI处理下山黧豆平均籽粒产量分别比FI处理显著降低了53%和63%。研究发现,在干旱胁迫条件下,山黧豆能够通过提高深层土壤中根系的比例、更多吸收深层土壤水分、显著增加根冠比以及显著提高生殖生长期叶片的瞬时水分利用效率,减轻干旱胁迫对自身生长的影响。该研究结果可为山黧豆在旱区推广种植提供理论依据。     

Purification and characterization of a novel keto ester reductase from the green alga, <Emphasis Type="Italic">Chlorella sorokiniana</Emphasis>: comparison of enzymological properties with other microbial keto ester reductases

A novel keto ester reductase (Chlorella sorokiniana keto ester reductase, CSKER) from Chlorella sorokiniana SAG 211-8k cells was purified. The CSKER had a monomeric structure based on gel filtration chromatography (37 kDa) and SDS–polyacrylamide gel electrophoresis (34 kDa). The purified CSKER showed a high reducing activity with β-keto esters, in particular, ethyl 4-chloro-3-oxobutanoate and ethyl 2-chloro-3-oxobutanoate. However, the purified enzyme did not show any reducing activity with α-keto esters and 2-chlorobenzoylformamide (aromatic α-keto amide). The CSKER catalyzed the reduction of ethyl 4-chloro-3-oxobutanoate, ethyl 3-oxobutanoate, and methyl 3-oxobutanoate to the corresponding (R)-, (S)-, and (S)-hydroxy ester, respectively, with high enantioselectivity (>99% e.e.), respectively. Furthermore, the reduction of ethyl 2-methyl-3-oxobutanoate by CSKER exclusively yielded the corresponding syn-(2R, 3S)-hydroxy ester. The purified CSKER was inactive with NADH, used instead of NADPH. None of the keto ester-reducing enzymes already isolated from other microorganisms was identical to the CSKER. These results suggested that CSKER is a novel keto ester reductase that has not yet been reported.     

Highly selective anti-Prelog synthesis of optically active aryl alcohols by recombinant Escherichia coli expressing stereospecific alcohol dehydrogenase

Biocatalytic asymmetric synthesis has been widely used for preparation of optically active chiral alcohols as the important intermediates and precursors of active pharmaceutical ingredients. However, the available whole-cell system involving anti-Prelog specific alcohol dehydrogenase is yet limited. A recombinant Escherichia coli system expressing anti-Prelog stereospecific alcohol dehydrogenase from Candida parapsilosis was established as a whole-cell system for catalyzing asymmetric reduction of aryl ketones to anti-Prelog configured alcohols. Using 2-hydroxyacetophenone as the substrate, reaction factors including pH, cell status, and substrate concentration had obvious impacts on the outcome of whole-cell biocatalysis, and xylose was found to be an available auxiliary substrate for intracellular cofactor regeneration, by which (S)-1-phenyl-1,2-ethanediol was achieved with an optical purity of 97%e.e. and yield of 89% under the substrate concentration of 5 g/L. Additionally, the feasibility of the recombinant cells toward different aryl ketones was investigated, and most of the corresponding chiral alcohol products were obtained with an optical purity over 95%e.e. Therefore, the whole-cell system involving recombinant stereospecific alcohol dehydrogenase was constructed as an efficient biocatalyst for highly enantioselective anti-Prelog synthesis of optically active aryl alcohols and would be promising in the pharmaceutical industry.     

Genetic Structure of Cochliobolus sativus Populations Sampled from Roots and Leaves of Barley and Wheat in North Dakota

Common root rot (CRR) and spot blotch, caused by Cochliobolus sativus (Ito and Kurib.) Drechsl. ex Dast., are important diseases of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) worldwide. However, the population biology of C. sativus is still poorly understood. In this study, the genetic structure of three C. sativus populations, consisting of isolates sampled respectively from barley leaves (BL), barley roots (BR) and wheat roots (WR) in North Dakota, was analysed with amplified fragment length polymorphism (AFLP) markers. A total of 127 AFLP loci were generated among 208 C. sativus isolates analysed with three primer combinations. Gene diversity (H = 0.277–0.335) were high in all three populations. Genetic variation among C. sativus individuals within population accounted for 74%, whereas 26% of the genetic variation was explained among populations. Genetic differentiation was high (ØPT = 0.261, corrected = 0.39), whereas gene flow (Nm) ranged from 1.27 to 1.56 among the three populations analysed. The multilocus linkage disequilibrium (LD) (= 0.076–0.117) was moderate in C  sativus populations. Cluster analyses indicate that C. sativus populations differentiated according to the hosts (barley and wheat) and tissues (root and leaf) although generalists also exist in North Dakota. Crop breeding may benefit from combining genes for resistance against both specialists and generalists of C. sativus.     

Crystal structure and iterative saturation mutagenesis of ChKRED20 for expanded catalytic scope

ChKRED20 is an efficient and robust anti-Prelog ketoreductase that can catalyze the reduction of ketones to chiral alcohols as pharmaceutical intermediates with great industrial potential. To overcome its limitation on the bioreduction of ortho-substituted acetophenone derivatives, the X-ray crystal structure of the apo-enzyme of ChKRED20 was determined at a resolution of 1.85 Å and applied to the molecular modeling and reshaping of the catalytic cavity via three rounds of iterative saturation mutagenesis together with alanine scanning and recombination. The mutant Mut3B was achieved with expanded catalytic scope that covered all the nine substrates tested as compared with two substrates for the wild type. It exhibited 13–20-fold elevated k _cat/K _m values relative to the wild type or to the first gain-of-activity mutant, while retaining excellent stereoselectivity toward seven of the substrates (98–> 99% ee). Another mutant 29G10 displayed complementary selectivity for eight of the ortho-substituted acetophenone derivatives, with six of them delivering excellent stereoselectivity (90–99% ee). Its k _cat/K _m value toward 1-(2-fluorophenyl)ethanone was 5.6-fold of the wild type. The application of Mut3B in elevated substrate concentrations of 50–100 g/l was demonstrated in 50-ml reactions, achieving 75–> 99% conversion and > 99% ee.

     

Bacteriochlorophyll c monomers,dimers, and higher aggregates in dichloromethane,chloroform, and carbon tetrachloride

Bacteriochlorophyll c in vivo is a mixture of at least 5 homologs, all of which form aggregates in CH₂Cl₂, CHCl₃ and CCl₄. Three homologs exist mainly in the 2-R-(1-hydroxyethyl) configuration, whereas the other two homologs, 4-isobutyl-5-ethyl and 4-isobutyl-5-methyl farnesyl bacteriochlorophyll c, exist mainly in the 2-S-(1-hydroxyethyl) configuration (Smith KM, Craig GW, Kehres LA and Pfennig N (1983) J. Chromatograph. 281: 209–223). In CCl₄ the S-homologs form an aggregate of 2–3 molecules whose absorption (747 nm maximum) and circular dichroism spectra resemble those of the chlorosome. In CH₂Cl₂, CHCl₃ and CCl₄ the 4-n-propyl homolog (R-configuration) forms dimers absorbing at ca. 680 nm and higher aggregates absorbing at 705–710 nm. In CCl₄ the dimerization constant is approx. 10 µM^–1 (1000 times that for chlorophyll a). The difference between the types of aggregates formed by the 4-n-propyl and 4-isobutyl homologs is attributed to the difference between the R- and S-configurations of the 2-(1-hydroxyethyl) groups in each chlorophyll.Abbreviations BChl bacteriochlorophyll - CD circular dichroism - Chl chlorophyll - DNS data not shown - EEF 4-ethyl-5-ethyl farnesyl - iBM/EF 4-isobutyl-5-methyl/ethyl farnesyl - MEF 4-methyl-5-ethyl farnesyl - PEP 4-n-propyl-5-ethyl farnesyl     

Lipase-catalyzed reaction in the packed-bed reactor with continuous extraction column to overcome a product inhibition

The resolution of rac-α-methyl-β-propiothiolactone (rac-MPTL) was performed in a packed-bed reactor (PBR) using Pseudomonas cepacia lipase (PCL) in organic media to produce enantiopure (R)-MPTL. By comparing enzyme stability of three enzyme forms, i.e. commercial PCL powder, Celite-immobilized PCL, and cross-linked enzyme crystals of PCL (CLECs-PCL), Celite-immobilized PCL was chosen for the construction of PBR because of its comparable stability to that of CLEC and easy handling. Owing to the severe product inhibition by 3-mercapto-α-methylpropionic acid (MMPA), the batch reaction system was inappropriate for the hydrolysis with PCL at high concentration of rac-MPTL. To overcome these problems, PBR with a continuous extraction column was used. The product inhibition was successfully overcome by incorporating an aqueous extraction unit. However, the yield of (R)-MPTL (enantiomeric excess, ee>99%) was only about 20% based upon the initial concentration of rac-MPTL, due to the concomitant partitioning of rac-MPTL to the aqueous phase in the extraction column as well as the subsequent auto-hydrolysis of rac-MPTL to rac-MMPA during extraction. To reduce the undesired partitioning of rac-MPTL to aqueous phase, various salts were screened to modulate the partitioning coefficient of the reaction components. Using 1 M ammonium sulfate solution as the aqueous phase of the extraction column, the yield of (R)-MPTL (ee>99%) was enhanced to 40%.     

Aggregation of bacteriochlorophyll c homologs to dimers,tetramers, and polymers in water-saturated carbon tetrachloride

Three homologs of BChl c, 2-(R)-(1-hydroxyethyl)-4-n-propyl-5-ethyl-farnesyl BChl c (PEF-BChl c), 2-(R)-(1-hydroxyethyl)-4-ethyl-5-ethyl-farnesyl BChl c (EEF-BChl c), and 2-(S)-(1-hydroxyethyl)-4-isobutyl-5-methyl/ethyl-farnesyl BChl c (iBM/EF-BChl c), formed aggregates in water-saturated carbon tetrachloride (H₂O-satd CCl₄). The water content was about 100 times higher than that of the dried CCl₄ previously used. Absorption spectra were recorded for 8 concentrations for the three homologs of BChl c and were deconvoluted in terms of standard spectra of monomer, dimer, tetramer and polymer (747-nm aggregate, Olson and Pedersen (1990) Photosynthe Res 25: 25). PEF- and EEF-BChl c formed dimers (680 nm maximum) and tetramers (705–710 nm maximum), but iBM/EF-BChl c formed polymers. Inhibition of dimer formation by water faciliated the study of the initial stages of the polymerization of BChl c. When the logarithm of polymer concentration was plotted versus the logarithm of the monomer concentration for iBM/EF-BChl c, the initial slope was 30±10 and indicated the cooperation of 20–40 BChl c molecules to form a polymer from a seed. Circular dichroism spectra of the polymers with positive and negative bands at 743 and 760 nm, respectively, were similar to those for chlorosomes (Brune et al. (1990) Photosynth Res 24: 253).Abbreviations BChl bacteriochlorophyll - CD circular dichroism - EEF 4-ethyl-5-ethyl farnesyl - iBM/EF 4-isobutyl-5-methyl/ethyl farnesyl - H₂O-satd CCl₄ water saturated carbon tetrachloride - PEF 4-n-propyl-5-ethyl farnesyl     

Cross-linked protein complex exhibiting asymmetric oxidation activities in the absence of added cofactor

A protein complex (PC) suspension exhibits asymmetric biooxidation activities in the absence of any added cofactor such as NAD(P)⁺ or FAD. It can be extracted from pea protein (PP)‐gel (PP encapsulated with Ca²⁺ alginate gel and aerated in air for several hours) using hot water by rotary shaking and powdered by the following three steps: (1) forming precipitates from the suspension using 30% (w/v) aqueous (NH₄)₂SO₄, (2) crosslinking the precipitates with 0.25% (v/v) GA, and (3) preparing the cross‐linked powder by freeze‐drying. The cross‐linked PC (CLPC) performed asymmetric oxidation of the toward (R)‐isomers of rac‐ 1 and rac ‐2 in 50 mM glycine–NaOH (pH 9.0) buffer/DMSO cosolvent [2.07% (v/v)] with high enantioselectivity; thus, the (S)‐isomers can be obtained in greater than 99% ee from the corresponding rac‐p‐substituted naphthyl methyl carbinol (rac‐ 1 and rac ‐2 ). The CLPC activity was not only competitively inhibited by addition of either 1.0 mM ZnCl₂ or a chelating agent such as 1.0 mM EDTA but also denatured by pretreatments: autoclaving at 121°C (20 min) or using 6.0 M guanidine–HCl containing 50 mM DTT. These results indicated that the PC catalytic process may utilize an electron transfer system incorporating a redox cation (e.g., Fe²⁺ ? Fe³⁺ or Zn). Therefore, the newly introduced CLPC can asymmetrically oxidize the substrates without the addition of any cofactor resulting in a low‐cost organic method. Overall, our results show that the CLPC is an easily prepared, low‐cost reagent that can function under mild conditions and afford stereoselectivity, regioselectivity, and substrate specificity. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 953–961, 2012     

Purification and characterization of an anti-Prelog alcohol dehydrogenase from <Emphasis Type="Italic">Oenococcus oeni</Emphasis> that reduces 2-octanone to (<Emphasis Type="Italic">R</Emphasis>)-2-octanol

An anti-Prelog alcohol dehydrogenase from Oenococcus oeni that reduces 2-octanone to (R)-2-octanol was purified by 26-fold to homogeneity. The enzyme had a homodimeric structure consisting of 49 kDa subunits, required NADPH, but not NADH, as a cofactor and was a Zn-independent short-chain dehydrogenase. Aliphatic methyl ketones (chain length ≥6 carbon atoms) and aromatic methyl ketones were the preferred substrates for the enzyme, the best being 2-octanone. Maximum enzyme activity with 2-octanone was at 45°C and at pH 8.0.     

Acetophenone superior to verbenone for reducing attraction of western pine beetle Dendroctonus brevicomis to its aggregation pheromone

1 The western pine beetle Dendroctonus brevicomis LeConte (Coleoptera: Scolytidae) is one of the most damaging insect pests of ponderosa pines Pinus ponderosa Douglas ex P. & C. Lawson in Western U.S.A. We compared the effect of verbenone, a well known bark beetle anti‐aggregation pheromone, with that of acetophenone on the attraction of D. brevicomis to its aggregation pheromone in a ponderosa pine forest in northern California. We tested the D. brevicomis aggregation pheromone alone and with three different release ratios of the aggregation pheromone (attractant) to verbenone or acetophenone (1 : 1, 1 : 2 and 1 : 5). 2 All treatments containing acetophenone or verbenone resulted in a significant reduction in the catch of D. brevicomis relative to the aggregation pheromone alone. When beetle responses to the three verbenone or three acetophenone treatments were pooled, the pooled verbenone treatment caught more D. brevicomis than the pooled acetophenone treatment. 3 There was no significant difference in the number of D. brevicomis caught among the three release rates of verbenone. By contrast, the 1 : 2 attractant : acetophenone ratio attracted significantly more D. brevicomis than the traps with the 1 : 5 attractant : acetophenone ratio. 4 Attraction of a major predator, Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), to the aggregation pheromone of D. brevicomis was reduced by verbenone, but not by acetophenone. Moreover, the T. chlorodia : D. brevicomis ratio for the pooled acetophenone treatment was 1.7‐fold greater than that for the attractant alone and two‐fold greater than the ratio for the pooled verbenone treatment, suggesting that acetophenone would not disrupt populations of this natural enemy. The importance of anti‐attractants in the biology of D. brevicomis and other bark beetles is discussed.     

Reduction of acetophenone to R(+)-phenylethanol by a new alcohol dehydrogenase from Lactobacillus kefir

Summary A new alcohol dehydrogenase catalysing the enantioselective reduction of acetophenone to R(+)-phenylethanol was found in a strain of Lactobacillus kefir. A 70-fold enrichment of the enzyme with an overall yield of 76% was obtained in two steps. The addition of Mg²⁺ ions was found to be necessary to prevent rapid deactivation. The enzyme depends essentially on NADPH and was inactive when supplied with NADH as the coenzyme. Important enzymological data of the dehydrogenase are: K _m (acetophenone) 0.6 mM, K _m (NADPH) 0.14 mM, and a pH optimum for acetophenone reduction at 7.0. Addition of EDTA leads to complete deactivation of the enzyme activity. Added iodoacetamide or p-hydroxymercuribenzoate cause only slight inhibition, revealing that the active centre of the enzyme contains no essential SH-group. Besides acetophenone several other aromatic and long-chain aliphatic secondary ketones are substrates for this enzyme. Batch production of phenylethanol was examined using three different methods for the regeneration of NADPH: glucose/glucose dehydrogenase, glucose-6-phosphate/glucose-6-phosphate dehydrogenase, and isopropanol.     

Reduction and cyclization in biotransformation of carbonyl compounds by cultured cells of Taxus species

Cultured plant cells from Taxus brevifolia Nutt and Taxus globosa Schltdl were investigated as biocatalysts using exogenous substrates. Production of highly specific metabolites by these species prompted us to analyse their synthetic potential. Whole cells suspensions have the capacity to chemoselectively reduce ethyl acetoacetate to ethyl 3-hydroxybutyrate chemo- and stereoselectively reduce rac-2-benzoylcyclohexanone to (1R, 2S)- and (1S, 2S)-2-hydroxycyclohexylphenylmethanones, and to cyclize N-phthaloyl-L-glutamine to thalidomide.     

Morphology and colonization preference of arbuscular mycorrhizal fungi in <Emphasis Type="Italic">Clethra barbinervis</Emphasis>, <Emphasis Type="Italic">Cucumis sativus</Emphasis>, and <Emphasis Type="Italic">Lycopersicon esculentum</Emphasis>

Clethra barbinervis (Ericales), Cucumis sativus, and Lycopersicon esculentum were grown in soils collected from six different vegetation sites (cedar, cypress, larch, red pine, bamboo grass, and Italian ryegrass), and morphology and colonization preference of arbuscular mycorrhizal (AM) fungi were investigated by microscopic observation and PCR detection. C. barbinervis consistently formed Paris-type AM throughout the sites. C. sativus formed both Arum- and Paris-type AM with high occurrence of Arum-type AM. L. esculentum also formed both Arum- and Paris-type AM but with high occurrence of Paris-type AM. AM diversity within the same plant species was different among the sites. Detected AM diversity from AM spores in different site soils did not consistently reflect AM fungal diversity seen in test plants. Detected families were different, depending on test plants grown even in the same soil. AM fungi belonging to Glomaceae were consistently detected from roots of all test plants throughout the sites. Almost all the families were detected from roots of C. barbinervis and L. esculentum. On the other hand, only two or three families of AM fungi (Archaeosporaceae and/or Paraglomaceae and Glomaceae) but not two other families (Acaulosporaceae and Gigasporaceae) were detected from roots of C. sativus, indicating strong colonization preference of AM fungi to C. sativus among test plants. This study demonstrated that host plant species strongly influenced the colonization preference of AM fungi in the roots.