The synthesis of (Z)-4-oxo-4-(arylamino)but-2-enoic acids derivatives and determination of their inhibition properties against human carbonic anhydrase I and II isoenzymes

The synthesis of (Z)-4-oxo-4-(arylamino)but-2-enoic acid (4) derivatives containing structural characteristics that can be used for the synthesis of several active molecules, is presented. Some of the butenoic acid derivatives (4a, 4c, 4e, 4i, 4j, 4k) are synthesized following literature procedures and at the end of the reaction. In addition, structures of all synthesized derivatives (4a-4m) were determined by (1)H-NMR, (13)C-NMR and IR spectroscopy. Carbonic anhydrase is a metalloenzyme involved in many crucial physiologic processes as it catalyzes a simple but fundamental reaction, the reversible hydration of carbon dioxide to bicarbonate and protons. Significant results were obtained by evaluating the enzyme inhibitory activities of these derivatives against human carbonic anhydrase hCA I and II isoenzymes (hCA I and II). Butenoic acid derivatives (4a-4m) strongly inhibited hCA I and II with Kis in the low nanomolar range of 1.85 ± 0.58 to 5.04 ± 1.46 nM against hCA I and in the range of 2.01 ± 0.52 to 2.94 ± 1.31 nM against hCA II.

UPF0586 Protein C9orf41 Homolog Is Anserine-producing Methyltransferase

Anserine (β-alanyl-N(Pi)-methyl-L-histidine), a methylated derivative of carnosine (β-alanyl-L-histidine), is an abundant constituent of vertebrate skeletal muscles. Although it has been suggested to serve as a proton buffer and radical scavenger, its physiological function remains mysterious. The formation of anserine is catalyzed by carnosine N-methyltransferase, recently identified in chicken as histamine N-methyltransferase-like (HNMT-like) protein. Although the HNMT-like gene is absent in mammalian genomes, the activity of carnosine N-methyltransferase was reported in most mammalian species. In the present investigation, we purified carnosine N-methyltransferase from rat muscles about 2600-fold. Three polypeptides of ∼ 45, 50, and 70 kDa coeluting with the enzyme activity were identified in the preparation. Mass spectrometry analysis of these polypeptides resulted in the identification of UPF0586 protein C9orf41 homolog as the only meaningful candidate. Rat UPF0586 and its yeast, chicken, and human orthologs were expressed in COS-7 cells and purified to homogeneity. Although all recombinant proteins catalyzed the formation of anserine, as confirmed by chromatographic and mass spectrometry analysis, rat UPF0586 was more active on carnosine than other orthologs. Confocal microscopy of HeLa cells expressing recombinant UPF5086 proteins revealed their presence in both cytosol and nucleus. Carnosine and Gly-His were the best substrates for all UPF0586 orthologs studied, although the enzymes also methylated other l-histidine-containing di- and tripeptides. Finally, cotransfection of COS-7 cells with rat or human UPF0586 and carnosine synthase transformed the cells into efficient anserine producers. We conclude that UPF0586 is mammalian carnosine N-methyltransferase and hypothesize that it may also serve as a peptide or protein methyltransferase in eukaryotes.

Application of an aqueous two-phase micellar system to extract bromelain from pineapple (Ananas comosus) peel waste and analysis of bromelain stability in cosmetic formulations

Bromelain is a set of proteolytic enzymes found in pineapple (Ananas comosus) tissues such as stem, fruit and leaves. Because of its proteolytic activity, bromelain has potential applications in the cosmetic, pharmaceutical, and food industries. The present study focused on the recovery of bromelain from pineapple peel by liquid-liquid extraction in aqueous two-phase micellar systems (ATPMS), using Triton X-114 (TX-114) and McIlvaine buffer, in the absence and presence of electrolytes CaCl2 and KI; the cloud points of the generated extraction systems were studied by plotting binodal curves. Based on the cloud points, three temperatures were selected for extraction: 30, 33, and 36°C for systems in the absence of salts; 40, 43, and 46°C in the presence of KI; 24, 27, and 30°C in the presence of CaCl2 . Total protein and enzymatic activities were analyzed to monitor bromelain. Employing the ATPMS chosen for extraction (0.5 M KI with 3% TX-114, at pH 6.0, at 40°C), the bromelain extract stability was assessed after incorporation into three cosmetic bases: an anhydrous gel, a cream, and a cream-gel formulation. The cream-gel formulation presented as the most appropriate base to convey bromelain, and its optimal storage conditions were found to be 4.0 ± 0.5°C. The selected ATPMS enabled the extraction of a biomolecule with high added value from waste lined-up in a cosmetic formulation, allowing for exploration of further cosmetic potential.

Doing that thing that scientists do: A discovery-driven module on protein purification and characterization for the undergraduate biochemistry laboratory classroom

In traditional introductory biochemistry laboratory classes students learn techniques for protein purification and analysis by following provided, established, step-by-step procedures. Students are exposed to a variety of biochemical techniques but are often not developing procedures or collecting new, original data. In this laboratory module, students develop research skills through work on an original research project and gain confidence in their ability to design and execute an experiment while faculty can enhance their scholarly pursuits through the acquisition of original data in the classroom laboratory. Students are prepared for a 6-8 week discovery-driven project on the purification of the Escherichia coli cytidylate kinase (CMP kinase) through in class problems and other laboratory exercises on bioinformatics and protein structure analysis. After a minimal amount of guidance on how to perform the CMP kinase in vitro enzyme assay, SDS-PAGE, and the basics of protein purification, students, working in groups of three to four, develop a protein purification protocol based on the scientific literature and investigate some aspect of CMP kinase that interests them. Through this process, students learn how to implement a new but perhaps previously worked out procedure to answer their research question. In addition, they learn the importance of keeping a clear and thorough laboratory notebook and how to interpret their data and use that data to inform the next set of experiments. Following this module, students had increased confidence in their ability to do basic biochemistry techniques and reported that the "self-directed" nature of this lab increased their engagement in the project.

Acetylcholinesterase and carbonic anhydrase isoenzymes I and II inhibition profiles of taxifolin

Taxifolin, also known as dihydroquercetin, is a flavonoid commonly found in plants. Carbonic anhydrase (CA, EC 4.2.1.1) plays an important role in many critical physiological events including carbon dioxide (CO2)/bicarbonate (HCO3(-)) respiration and pH regulation. There are 16 known CA isoforms in humans, of which human hCA isoenzymes I and II (hCA I and II) are ubiquitous cytosolic isoforms. In this study, the inhibition properties of taxifolin against the slow cytosolic isoenzyme hCA I, and the ubiquitous and dominant rapid cytosolic isoenzyme hCA II were studied. Taxifolin, as a naturally bioactive flavonoid, has a K(i) of 29.2 nM against hCA I, and 24.2 nM against hCA II. For acetylcholinesterase enzyme (AChE) inhibition, K(i) parameter of taxifolin was determined to be 16.7 nM. These results clearly show that taxifolin inhibited both CA isoenzymes and AChE at the nM levels.

Isolation and Characterization of a Hybrid Respiratory Supercomplex Consisting of Mycobacterium tuberculosis Cytochrome bcc and Mycobacterium smegmatis Cytochrome aa3

Recently, energy production pathways have been shown to be viable antitubercular drug targets to combat multidrug-resistant tuberculosis and eliminate pathogen in the dormant state. One family of drugs currently under development, the imidazo[1,2-a]pyridine derivatives, is believed to target the pathogen's homolog of the mitochondrial bc1 complex. This complex, denoted cytochrome bcc, is highly divergent from mitochondrial Complex III both in subunit structure and inhibitor sensitivity, making it a good target for drug development. There is no soluble cytochrome c in mycobacteria to transport electrons from the bcc complex to cytochrome oxidase. Instead, the bcc complex exists in a "supercomplex" with a cytochrome aa3-type cytochrome oxidase, presumably allowing direct electron transfer. We describe here purification and initial characterization of the mycobacterial cytochrome bcc-aa3 supercomplex using a strain of M. smegmatis that has been engineered to express the M. tuberculosis cytochrome bcc. The resulting hybrid supercomplex is stable during extraction and purification in the presence of dodecyl maltoside detergent. It is hoped that this purification procedure will potentiate functional studies of the complex as well as crystallographic studies of drug binding and provide structural insight into a third class of the bc complex superfamily.

Functionalized anodic aluminum oxide membrane-electrode system for enzyme immobilization

A nanoporous membrane system with directed flow carrying reagents to sequentially attached enzymes to mimic nature’s enzyme complex system was demonstrated. Genetically modified glycosylation enzyme, OleD Loki variant, was immobilized onto nanometer-scale electrodes at the pore entrances/exits of anodic aluminum oxide membranes through His6-tag affinity binding. The enzyme activity was assessed in two reactions—a one-step “reverse” sugar nucleotide formation reaction (UDP-Glc) and a two-step sequential sugar nucleotide formation and sugar nucleotide-based glycosylation reaction. For the one-step reaction, enzyme specific activity of 6–20 min(–1) on membrane supports was seen to be comparable to solution enzyme specific activity of 10 min(–1). UDP-Glc production efficiencies as high as 98% were observed at a flow rate of 0.5 mL/min, at which the substrate residence time over the electrode length down pore entrances was matched to the enzyme activity rate. This flow geometry also prevented an unwanted secondary product hydrolysis reaction, as observed in the test homogeneous solution. Enzyme utilization increased by a factor of 280 compared to test homogeneous conditions due to the continuous flow of fresh substrate over the enzyme. To mimic enzyme complex systems, a two-step sequential reaction using OleD Loki enzyme was performed at membrane pore entrances then exits. After UDP-Glc formation at the entrance electrode, aglycon 4-methylumbelliferone was supplied at the exit face of the reactor, affording overall 80% glycosylation efficiency. The membrane platform showed the ability to be regenerated with purified enzyme as well as directly from expression crude, thus demonstrating a single-step immobilization and purification process.

Extraction, purification, kinetic and thermodynamic properties of urease from germinating Pisum Sativum L. seeds

BACKGROUND

Urease, one of the highly efficient known enzymes, catalyzes the hydrolysis of urea into ammonia and carbon dioxide. The present study aimed to extract urease from pea seeds (Pisum Sativum L). The enzyme was then purified in three consequence steps: acetone precipitation, DEAE-cellulose ion-exchange chromatography, and gel filtration chromatography (Sephacryl S-200 column).

RESULTS

The purification fold was 12.85 with a yield of 40%. The molecular weight of the isolated urease was estimated by chromatography to be 269,000 Daltons. Maximum urease activity (190 U/g) was achieved at the optimum conditions of 40°C and pH of 7.5 after 5 min of incubation. The kinetic parameters, Km and Vmax, were estimated by Lineweaver-Burk fits and found to be 500 mM and 333.3 U/g, respectively. The thermodynamic constants of activation, ΔH, Ea, and ΔS, were determined using Arrhenius plot and found to be 21.20 kJ/mol, 23.7 kJ/mol, and 1.18 kJ/mol/K, respectively.

CONCLUSIONS

Urease was purified from germinating Pisum Sativum L. seeds. The purification fold, yield, and molecular weight were determined. The effects of pH, concentration of enzyme, temperature, concentration of substrate, and storage period on urease activity were examined. This may provide an insight on the various aspects of the property of the enzyme. The significance of extracting urease from different sources could play a good role in understanding the metabolism of urea in plants.

Isolation and enzymatic properties of a nonspecific acid phosphatase from Vigna aconitifolia seeds

Acid phosphatase (EC 3.1.3.2) from Vigna aconitifolia seeds was purified to apparent homogeneity by using ammonium sulfate fractionation and cation-exchange chromatography [carboxymethyl (CM) cellulose]. The enzyme was 228-fold purified with 14.6% recovery. Analytical gel filtration chromatography on Sephadex G-200 column showed that Mr of native enzyme was 58 kDa and denaturing PAGE demonstrated that it was made up of two subunits of 24 and 27 kDa. The enzyme showed its optimum activity at pH 5.0 and 60°C. It exhibited broad substrate specificity and showed a higher specificity constant for para-nitrophenyl phosphate, Na β-naphthyl phosphate, and adenosine monophosphate (AMP). Cu²⁺, Mo⁶⁺, Fe³⁺, phosphate, and fluoride ions were reported as strong inhibitors for the enzyme. Active site study for the enzyme demonstrated that tryptophan and aspartic acid may be important for the catalysis.

Comparative studies on acetylcholinesterase characteristics between the aphids, Sitobion avenae and Rhopalosiphum padi

The aphids Sitobion avenae (Fabricius) and Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphidiae) are serious pests on grain crops and usually coexist on late period of wheat growth in China. Bioassays showed that R. padi was more susceptible than S. avenae to pirimicarb that is used for wheat aphid control, and the determination of acetylcholinesterase (AChE, EC 3.1.1.7) sensitivity showed that the sensitivity of AChE to pirimicarb was significantly higher in R. padi than in S. avenae ( Lu and Gao 2009 ). AChE is the target enzyme of the carbamates, including pirimicarb, hence, to understand the mechanism responsible for the tolerance difference to carbamate insecticides of S. avenae and R. padi, we purified AChE from both aphid species using procainamide affinity column and characterized the AChE. The purification factor and yield from S. avenae (234.7-fold and 92.9%) were far higher than that from R. padi 17.3-fold and 13.9%. The results of substrate and inhibitor specificities of purified enzyme from both S. avenae and R. padi indicated that the purified enzyme was a typical AChE. The crude AChE extract from S. avenae was 5.4-, 4.3- and 8.1-fold less sensitive to inhibition by pirimicarb, methomyl and thiodicarb, respectively, than that from R. padi, whereas for the purified AChE, S. avenae was only 1.6-, 1.3- and 1.7-fold less sensitive to inhibition by pirimicarb, methomyl and thiodicarb, respectively, than R. padi. This suggests that eserine and BW284C51 may bind with other proteins, such as carboxylesterase, in the crude extract to reduce their inhibition against AChE. These results are useful for planning the chemical control of aphids on wheat.

An L-glucose catabolic pathway in Paracoccus species 43P

BACKGROUND

L-Glucose, the enantiomer of D-glucose, was believed not to be utilized by any organisms.

RESULTS

An L-glucose-utilizing bacterium was isolated, and its L-glucose catabolic pathway was identified genetically and enzymatically.

CONCLUSION

L-Glucose was utilized via a novel pathway to pyruvate and D-glyceraldehyde 3-phosphate.

SIGNIFICANCE

This might lead to an understanding of homochirality in sugar metabolism. An L-glucose-utilizing bacterium, Paracoccus sp. 43P, was isolated from soil by enrichment cultivation in a minimal medium containing L-glucose as the sole carbon source. In cell-free extracts from this bacterium, NAD(+)-dependent L-glucose dehydrogenase was detected as having sole activity toward L-glucose. This enzyme, LgdA, was purified, and the lgdA gene was found to be located in a cluster of putative inositol catabolic genes. LgdA showed similar dehydrogenase activity toward scyllo- and myo-inositols. L-Gluconate dehydrogenase activity was also detected in cell-free extracts, which represents the reaction product of LgdA activity toward L-glucose. Enzyme purification and gene cloning revealed that the corresponding gene resides in a nine-gene cluster, the lgn cluster, which may participate in aldonate incorporation and assimilation. Kinetic and reaction product analysis of each gene product in the cluster indicated that they sequentially metabolize L-gluconate to glycolytic intermediates, D-glyceraldehyde-3-phosphate, and pyruvate through reactions of C-5 epimerization by dehydrogenase/reductase, dehydration, phosphorylation, and aldolase reaction, using a pathway similar to L-galactonate catabolism in Escherichia coli. Gene disruption studies indicated that the identified genes are responsible for L-glucose catabolism.

X-linked sideroblastic anemia due to carboxyl-terminal ALAS2 mutations that cause loss of binding to the β-subunit of succinyl-CoA synthetase (SUCLA2)

Mutations in the erythroid-specific aminolevulinic acid synthase gene (ALAS2) cause X-linked sideroblastic anemia (XLSA) by reducing mitochondrial enzymatic activity. Surprisingly, a patient with the classic XLSA phenotype had a novel exon 11 mutation encoding a recombinant enzyme (p.Met567Val) with normal activity, kinetics, and stability. Similarly, both an expressed adjacent XLSA mutation, p.Ser568Gly, and a mutation (p.Phe557Ter) lacking the 31 carboxyl-terminal residues also had normal or enhanced activity, kinetics, and stability. Because ALAS2 binds to the β subunit of succinyl-CoA synthetase (SUCLA2), the mutant proteins were tested for their ability to bind to this protein. Wild type ALAS2 bound strongly to a SUCLA2 affinity column, but the adjacent XLSA mutant enzymes and the truncated mutant did not bind. In contrast, vitamin B6-responsive XLSA mutations p.Arg452Cys and p.Arg452His, with normal in vitro enzyme activity and stability, did not interfere with binding to SUCLA2 but instead had loss of positive cooperativity for succinyl-CoA binding, an increased K(m) for succinyl-CoA, and reduced vitamin B6 affinity. Consistent with the association of SUCLA2 binding with in vivo ALAS2 activity, the p.Met567GlufsX2 mutant protein that causes X-linked protoporphyria bound strongly to SUCLA2, highlighting the probable role of an ALAS2-succinyl-CoA synthetase complex in the regulation of erythroid heme biosynthesis.

Purification and properties of S-hydroxymethylglutathione dehydrogenase of Paecilomyces variotii no. 5, a formaldehyde-degrading fungus

S-hydroxymethylglutathione dehydrogenase from Paecilomyces variotii No. 5 strain (NBRC 109023), isolated as a formaldehyde-degrading fungus, was purified by a procedure that included ammonium sulfate precipitation, DEAE-Sepharose and hydroxyapatite chromatography and isoelectrofocusing. Approximately 122-fold purification was achieved with a yield of 10.5%. The enzyme preparation was homogeneous as judged by sodium dodecyl polyacrylamide gel electrophoresis (SDS-PAGE). The molecular mass of the purified enzyme was estimated to be 49 kDa by SDS-PAGE and gel filtration, suggesting that it is a monomer. Enzyme activity was optimal at pH 8.0 and was stable in the range of pH 7.0-10. The optimum temperature for activity was 40°C and the enzyme was stable up to 40°C. The isoelectric point was pH 5.8. Substrate specificity was very high for formaldehyde. Besides formaldehyde, the only aldehyde or alcohol tested that served as a substrate was pyruvaldehyde. Enzyme activity was enhanced by several divalent cations such as Mn2+ (179%), Ba2+ (132%), and Ca2+ (112%) but was completely inhibited by Ni2+, Fe3+, Hg2+, p-chloromercuribenzoate (PCMB) and cuprizone. Inactivation of the enzyme by sulfhydryl reagents (Hg2+ and PCMB) indicated that the sulfhydryl group of the enzyme is essential for catalytic activity.

Novel dextranase catalyzing cycloisomaltooligosaccharide formation and identification of catalytic amino acids and their functions using chemical rescue approach

A novel endodextranase from Paenibacillus sp. (Paenibacillus sp. dextranase; PsDex) was found to mainly produce isomaltotetraose and small amounts of cycloisomaltooligosaccharides (CIs) with a degree of polymerization of 7-14 from dextran. The 1,696-amino acid sequence belonging to the glycosyl hydrolase family 66 (GH-66) has a long insertion (632 residues; Thr(451)-Val(1082)), a portion of which shares identity (35% at Ala(39)-Ser(1304) of PsDex) with Pro(32)-Ala(755) of CI glucanotransferase (CITase), a GH-66 enzyme that catalyzes the formation of CIs from dextran. This homologous sequence (Val(837)-Met(932) for PsDex and Tyr(404)-Tyr(492) for CITase), similar to carbohydrate-binding module 35, was not found in other endodextranases (Dexs) devoid of CITase activity. These results support the classification of GH-66 enzymes into three types: (i) Dex showing only dextranolytic activity, (ii) Dex catalyzing hydrolysis with low cyclization activity, and (iii) CITase showing CI-forming activity with low dextranolytic activity. The fact that a C-terminal truncated enzyme (having Ala(39)-Ser(1304)) has 50% wild-type PsDex activity indicates that the C-terminal 392 residues are not involved in hydrolysis. GH-66 enzymes possess four conserved acidic residues (Asp(189), Asp(340), Glu(412), and Asp(1254) of PsDex) of catalytic candidates. Their amide mutants decreased activity (1⁄1,500 to 1⁄40,000 times), and D1254N had 36% activity. A chemical rescue approach was applied to D189A, D340G, and E412Q using α-isomaltotetraosyl fluoride with NaN(3). D340G or E412Q formed a β- or α-isomaltotetraosyl azide, respectively, strongly indicating Asp(340) and Glu(412) as a nucleophile and acid/base catalyst, respectively. Interestingly, D189A synthesized small sized dextran from α-isomaltotetraosyl fluoride in the presence of NaN(3).

Fungal ecdysteroid-22-oxidase, a new tool for manipulating ecdysteroid signaling and insect development

Steroid hormones ecdysteroids regulate varieties of developmental processes in insects. Although the ecdysteroid titer can be increased experimentally with ease, its artificial reduction, although desirable, is very difficult to achieve. Here we characterized the ecdysteroid-inactivating enzyme ecdysteroid-22-oxidase (E22O) from the entomopathogenic fungus Nomuraea rileyi and used it to develop methods for reducing ecdysteroid titer and thereby controlling insect development. K(m) and K(cat) values of the purified E22O for oxidizing ecdysone were 4.4 μM and 8.4/s, respectively, indicating that E22O can inactivate ecdysone more efficiently than other ecdysteroid inactivating enzymes characterized so far. The cloned E22O cDNA encoded a FAD-dependent oxidoreductase. Injection of recombinant E22O into the silkworm Bombyx mori interfered with larval molting and metamorphosis. In the hemolymph of E22O-injected pupae, the titer of hormonally active 20-hydroxyecdysone decreased and concomitantly large amounts of inactive 22-dehydroecdysteroids accumulated. E22O injection also prevented molting of various other insects. In the larvae of the crambid moth Haritalodes basipunctalis, E22O injection induced a diapause-like developmental arrest, which, as in normal diapause, was broken by chilling. Transient expression of the E22O gene by in vivo lipofection effectively decreased the 20-hydroxyecdysone titer and blocked molting in B. mori. Transgenic expression of E22O in Drosophila melanogaster caused embryonic morphological defects, phenotypes of which were very similar to those of the ecdysteroid synthesis deficient mutants. Thus, as the first available simple but versatile tool for reducing the internal ecdysteroid titer, E22O could find use in controlling a broad range of ecdysteroid-associated developmental and physiological phenomena.

Human α/β hydrolase domain containing 10 (ABHD10) is responsible enzyme for deglucuronidation of mycophenolic acid acyl-glucuronide in liver

Mycophenolic acid (MPA), the active metabolite of the immunosuppressant mycophenolate mofetil (MMF), is primarily metabolized by glucuronidation to a phenolic glucuronide (MPAG) and an acyl glucuronide (AcMPAG). It is known that AcMPAG, which may be an immunotoxic metabolite, is deglucuronidated in human liver. However, it has been reported that recombinant β-glucuronidase does not catalyze this reaction. AcMPAG deglucuronidation activity was detected in both human liver cytosol (HLC) and microsomes (HLM). In this study, the enzyme responsible for AcMPAG deglucuronidation was identified by purification from HLC with column chromatographic purification steps. The purified enzyme was identified as α/β hydrolase domain containing 10 (ABHD10) by amino acid sequence analysis. Recombinant ABHD10 expressed in Sf9 cells efficiently deglucuronidated AcMPAG with a K(m) value of 100.7 ± 10.2 μM, which was similar to those in HLM, HLC, and human liver homogenates (HLH). Immunoblot analysis revealed ABHD10 protein expression in both HLC and HLM. The AcMPAG deglucuronidation by recombinant ABHD10, HLC, and HLH were potently inhibited by AgNO(3), CdCl(2), CuCl(2), PMSF, bis-p-nitrophenylphosphate, and DTNB. The CL(int) value of AcMPAG formation from MPA, which was catalyzed by human UGT2B7, in HLH was increased by 1.8-fold in the presence of PMSF. Thus, human ABHD10 would affect the formation of AcMPAG, the immunotoxic metabolite.

Biochemical and molecular characterization of secreted α-xylosidase from Aspergillus niger

α-Linked xylose is a major component of xyloglucans in the cell walls of higher plants. An α-xylosidase (AxlA) was purified from a commercial enzyme preparation from Aspergillus niger, and the encoding gene was identified. The protein is a member of glycosyl hydrolase family 31. It was active on p-nitrophenyl-α-d-xyloside, isoprimeverose, xyloglucan heptasaccharide (XXXG), and tamarind xyloglucan. When expressed in Pichia pastoris, AxlA had activity comparable to the native enzyme on pNPαX and IP despite apparent hyperglycosylation. The pH optimum of AxlA was between 3.0 and 4.0. AxlA together with β-glucosidase depolymerized xyloglucan heptasaccharide. A combination of AxlA, β-glucosidase, xyloglucanase, and β-galactosidase in the optimal proportions of 51:5:19:25 or 59:5:11:25 could completely depolymerize tamarind XG to free Glc or Xyl, respectively. To the best of our knowledge, this is the first characterization of a secreted microbial α-xylosidase. Secreted α-xylosidases appear to be rare in nature, being absent from other tested commercial enzyme mixtures and from the genomes of most filamentous fungi.

Ulvan lyases isolated from the Flavobacteria Persicivirga ulvanivorans are the first members of a new polysaccharide lyase family

Ulvans are complex sulfated polysaccharides found in the cell walls of green algae belonging to the genus Ulva. These polysaccharides are composed of disaccharide repetition moieties made up of sulfated rhamnose linked to either glucuronic acid, iduronic acid, or xylose. Two ulvan lyases of 30 and 46 kDa were purified from the culture supernatant of Persicivirga ulvanivorans. Based on peptide sequencing, the gene encoding the 46-kDa ulvan lyase was cloned. Sequence analysis revealed that the protein is modular and possesses a catalytic module similar to that of the 30-kDa ulvan lyase along with a module of unknown function. The ulvan-degrading function of the gene was confirmed by expression of the catalytic module in a heterologous system. The gene encoding the catalytic module has no sequence homolog in sequence databases and is likely to be the first member of a novel polysaccharide lyase family. Analysis of degradation products showed that both the 30- and 46-kDa ulvan lyases are endolytic and cleave the glycosidic bond between the sulfated rhamnose and a glucuronic or iduronic acid.

Characterization of a novel β-L-Arabinofuranosidase in Bifidobacterium longum: functional elucidation of A DUF1680 family member

Pfam DUF1680 (PF07944) is an uncharacterized protein family conserved in many species of bacteria, actinomycetes, fungi, and plants. In a previous article, we cloned and characterized the hypBA2 gene as a β-l-arabinobiosidase in Bifidobacterium longum JCM 1217. In this study, we cloned a DUF1680 family member, the hypBA1 gene, which constitutes a gene cluster with hypBA2. HypBA1 is a novel β-l-arabinofuranosidase that liberates l-arabinose from the l-arabinofuranose (Araf)-β1,2-Araf disaccharide. HypBA1 also transglycosylates 1-alkanols with retention of the anomeric configuration. Mutagenesis and azide rescue experiments indicated that Glu-366 is a critical residue for catalytic activity. This report provides the first characterization of a DUF1680 family member, which defines a new family of glycoside hydrolases, the GH family 127.

Substrate recognition and specificity of the NisB protein, the lantibiotic dehydratase involved in nisin biosynthesis

Nisin is a posttranslationally modified antimicrobial peptide containing the cyclic thioether amino acids lanthionine and methyllanthionine. Although much is known about its antimicrobial activity and mode of action, knowledge about the nisin modification process is still rather limited. The dehydratase NisB is believed to be the initial interaction partner in modification. NisB dehydrates specific serine and threonine residues in prenisin, whereas the cyclase NisC catalyzes the (methyl)lanthionine formation. The fully modified prenisin is exported and the leader peptide is cleaved off by the extracellular protease NisP. Light scattering analysis demonstrated that purified NisB is a dimer in solution. Using size exclusion chromatography and surface plasmon resonance, the interaction of NisB and prenisin, including several of its modified derivatives, was studied. Unmodified prenisin binds to NisB with an affinity of 1.05 ± 0.25 μm, whereas the dehydrated and the fully modified derivatives bind with respective affinities of 0.31 ± 0.07 and 10.5 ± 1.7 μm. The much lower affinity for the fully modified prenisin was related to a >20-fold higher off-rate. For all three peptides the stoichiometry of binding was 1:1. Active nisin, which is the equivalent of fully modified prenisin lacking the leader peptide did not bind to NisB, nor did prenisin in which the highly conserved FNLD box within the leader peptide was mutated to AAAA. Taken together our data indicate that the leader peptide is essential for initial recognition and binding of prenisin to NisB.

A trypsin-like protease in rice green semi-looper, Naranga aenescens Moore (Lepidoptera: Noctuidae): purification and characterization

The rice green semi looper, Naranga aenescens Moore (Lepidoptera: Noctuidae) causes severe damage to rice fields in Eastern Asia and Middle East. We demonstrate that two types of serine proteases are active in the midgut of the third instar larvae of N. aenescens, but trypsin-like proteases are considerably more active than chymotrypsin-like proteases. To develop better control strategies, purification and biochemical characterization of a major trypsin-like digestive protease from the midgut of the third instar larvae of N. aenescens was achieved by gel filtration and anion exchange chromatography. After the final purification step, the enzyme was purified 9.62-fold with a recovery of 16.1% and a specific activity of 4.12 U/mg protein and a molecular mass of approximately 88.5 kDa. Biochemical characterization indicated that the purified protease had highest activity at pH 10 and 30°C and was stable for up to 6 h under those conditions. Divalent cations, especially Ca2+, Mg2+, and Cu2+, increased the enzyme activity and synthetic inhibitors that target trypsin-like activity caused a significant reduction in caseinolytic activity. These data may be used to develop inhibitors that decrease the damage of N. aenescens to rice cultivars in the field.

Purification and identification of activating enzymes of CS-0777, a selective sphingosine 1-phosphate receptor 1 modulator, in erythrocytes

CS-0777 is a selective sphingosine 1-phosphate (S1P) receptor 1 modulator with potential benefits in the treatment of autoimmune diseases, including multiple sclerosis. CS-0777 is a prodrug that requires phosphorylation to an active S1P analog, similar to the first-in-class S1P receptor modulator FTY720 (fingolimod). We sought to identify the kinase(s) involved in phosphorylation of CS-0777, anticipating sphingosine kinase (SPHK) 1 or 2 as likely candidates. Unlike kinase activity for FTY720, which is found predominantly in platelets, CS-0777 kinase activity was found mainly in red blood cells (RBCs). N,N-Dimethylsphingosine, an inhibitor of SPHK1 and -2, did not inhibit CS-0777 kinase activity. We purified CS-0777 kinase activity from human RBCs by more than 10,000-fold using ammonium sulfate precipitation and successive chromatography steps, and we identified fructosamine 3-kinase (FN3K) and fructosamine 3-kinase-related protein (FN3K-RP) by mass spectrometry. Incubation of human RBC lysates with 1-deoxy-1-morpholinofructose, a competitive inhibitor of FN3K, inhibited ∼10% of the kinase activity, suggesting FN3K-RP is the principal kinase responsible for activation of CS-0777 in blood. Lysates from HEK293 cells overexpressing FN3K or FN3K-RP resulted in phosphorylation of CS-0777 and structurally related molecules but showed little kinase activity for FTY720 and no kinase activity for sphingosine. Substrate preference was highly correlated among FN3K, FN3K-RP, and rat RBC lysates. FN3K and FN3K-RP are known to phosphorylate sugar moieties on glycosylated proteins, but this is the first report that these enzymes can phosphorylate hydrophobic xenobiotics. Identification of the kinases responsible for CS-0777 activation will permit a better understanding of the pharmacokinetics and pharmacodynamics of this promising new drug.

A novel cold-active lipase from Candida albicans: cloning, expression and characterization of the recombinant enzyme

A novel lipase gene lip5 from the yeast Candida albicans was cloned and sequenced. Alignment of amino acid sequences revealed that 86-34% identity exists with lipases from other Candida species. The lipase and its mutants were expressed in the yeast Pichia pastoris, where alternative codon usage caused the mistranslation of 154-Ser and 293-Ser as leucine. 154-Ser to leucine resulted in loss of expression of Lip5, and 293-Ser to leucine caused a marked reduction in the lipase activity. Lip5-DM, which has double mutations that revert 154 and 293 to serine residues, showed good lipase activity, and was overexpressed and purified by (NH(4))(2)SO(4) precipitation and ion-exchange chromatography. The pure Lip5-DM was stable at low temperatures ranging from 15-35 °C and pH 5-9, with the optimal conditions being 15-25 °C and pH 5-6. The activation energy of recombinant lipase was 8.5 Kcal/mol between 5 and 25 °C, suggesting that Lip5-DM was a cold-active lipase. Its activity was found to increase in the presence of Zn(2+), but it was strongly inhibited by Fe(2+), Fe(3+), Hg(2+) and some surfactants. In addition, the Lip5-DM could not tolerate water-miscible organic solvents. Lip5-DM exhibited a preference for the short-and medium-chain length p-nitrophenyl (C4 and C8 acyl group) esters rather than the long chain length p-nitrophenyl esters (C12, C16 and C18 acyl group) with highest activity observed with the C8 derivatives. The recombinant enzyme displayed activity toward triacylglycerols, such as olive oil and safflower oil.

Identification and characterization of oxalate oxidoreductase, a novel thiamine pyrophosphate-dependent 2-oxoacid oxidoreductase that enables anaerobic growth on oxalate

Moorella thermoacetica is an anaerobic acetogen, a class of bacteria that is found in the soil, the animal gastrointestinal tract, and the rumen. This organism engages the Wood-Ljungdahl pathway of anaerobic CO(2) fixation for heterotrophic or autotrophic growth. This paper describes a novel enzyme, oxalate oxidoreductase (OOR), that enables M. thermoacetica to grow on oxalate, which is produced in soil and is a common component of kidney stones. Exposure to oxalate leads to the induction of three proteins that are subunits of OOR, which oxidizes oxalate coupled to the production of two electrons and CO(2) or bicarbonate. Like other members of the 2-oxoacid:ferredoxin oxidoreductase family, OOR contains thiamine pyrophosphate and three [Fe(4)S(4)] clusters. However, unlike previously characterized members of this family, OOR does not use coenzyme A as a substrate. Oxalate is oxidized with a k(cat) of 0.09 s(-1) and a K(m) of 58 μM at pH 8. OOR also oxidizes a few other 2-oxoacids (which do not induce OOR) also without any requirement for CoA. The enzyme transfers its reducing equivalents to a broad range of electron acceptors, including ferredoxin and the nickel-dependent carbon monoxide dehydrogenase. In conjunction with the well characterized Wood-Ljungdahl pathway, OOR should be sufficient for oxalate metabolism by M. thermoacetica, and it constitutes a novel pathway for oxalate metabolism.

Sulfoacetate is degraded via a novel pathway involving sulfoacetyl-CoA and sulfoacetaldehyde in Cupriavidus necator H16

Bacterial degradation of sulfoacetate, a widespread natural product, proceeds via sulfoacetaldehyde and requires a considerable initial energy input. Whereas the fate of sulfoacetaldehyde in Cupriavidus necator (Ralstonia eutropha) H16 is known, the pathway from sulfoacetate to sulfoacetaldehyde is not. The genome sequence of the organism enabled us to hypothesize that the inducible pathway, which initiates sau (sulfoacetate utilization), involved a four-gene cluster (sauRSTU; H16_A2746 to H16_A2749). The sauR gene, divergently orientated to the other three genes, probably encodes the transcriptional regulator of the presumed sauSTU operon, which is subject to inducible transcription. SauU was tentatively identified as a transporter of the major facilitator superfamily, and SauT was deduced to be a sulfoacetate-CoA ligase. SauT was a labile protein, but it could be separated and shown to generate AMP and an unknown, labile CoA-derivative from sulfoacetate, CoA, and ATP. This unknown compound, analyzed by MALDI-TOF-MS, had a relative molecular mass of 889.7, which identified it as protonated sulfoacetyl-CoA (calculated 889.6). SauS was deduced to be sulfoacetaldehyde dehydrogenase (acylating). The enzyme was purified 175-fold to homogeneity and characterized. Peptide mass fingerprinting confirmed the sauS locus (H16_A2747). SauS converted sulfoacetyl-CoA and NADPH to sulfoacetaldehyde, CoA, and NADP(+), thus confirming the hypothesis.

Human cytochrome P450 4F11: heterologous expression in bacteria, purification, and characterization of catalytic function

Human cytochrome P450 (P450) 4F11 is still considered an "orphan" because its function is not well characterized. A bacterial expression system was developed for human P450 4F11, producing approximately 230nmol P450 from a 3-l culture of Escherichia coli. P450 4F11 was purified and utilized for untargeted substrate searches in human liver extract using a liquid chromatography/mass spectrometry-based metabolomic and isotopic labeling approach (Tang et al., 2009 [19]). Four fatty acids-palmitic, oleic, arachidonic, and docosahexaenoic-were identified in human liver and verified as substrates of P450 4F11. The products were characterized as omega-hydroxylated fatty acids by gas chromatography-mass spectrometry analysis of their trimethylsilyl derivatives. Kinetic analysis of the oxidation products confirmed that the fatty acids are substrates oxidized by P450 4F11. P450 4F11 also exhibited low activity for some drug N-demethylation reactions but none for activation of several pro-carcinogens.

Characterization of a new beta(1-3)-glucan branching activity of Aspergillus fumigatus

A new HPLC method was developed to separate linear from beta(1-6)-branched beta(1-3)-glucooligosaccharides. This methodology has permitted the isolation of the first fungal beta(1-6)/beta(1-3)-glucan branching transglycosidase using a cell wall autolysate of Aspergillus fumigatus (Af). The encoding gene, AfBGT2 is an ortholog of AfBGT1, another transglycosidase of A. fumigatus previously analyzed (Mouyna, I., Hartland, R. P., Fontaine, T., Diaquin, M., Simenel, C., Delepierre, M., Henrissat, B., and Latgé, J. P. (1998) Microbiology 144, 3171-3180). Both enzymes release laminaribiose from the reducing end of a beta(1-3)-linked oligosaccharide and transfer the remaining chain to another molecule of the original substrate. The AfBgt1p transfer occurs at C-6 of the non-reducing end group of the acceptor, creating a kinked beta(1-3;1-6) linear molecule. The AfBgt2p transfer takes place at the C-6 of an internal group of the acceptor, resulting in a beta(1-3)-linked product with a beta(1-6)-linked side branch. The single Afbgt2 mutant and the double Afbgt1/Afbgt2 mutant in A. fumigatus did not display any cell wall phenotype showing that these activities were not responsible for the construction of the branched beta(1-3)-glucans of the cell wall.

Porphobilinogen synthase from the butterfly, Pieris brassicae: purification and comparative characterization

Porphobilinogen represents a key building block of tetrapyrroles serving as functional ligands of many vitally important proteins. Here we report the first purification of porphobilinogen synthase (PBGS) from whole insects by sequentially employing two modes of native electrophoresis on polyacrylamide gels subsequent to more conventional procedures. Using adults of Pieris brassicae L. (Lepidoptera: Pieridae) we achieved approximately 10,000-fold purification with final yields of up to 25% of electrophoretically pure PBGS with a specific activity of approximately 160 micromol PBG h(-1) mg(-1) at 37 degrees C and an affinity of 0.36 mM to its substrate 5-aminolevulinic acid. Enzyme activity was inhibited by the substrate mimics, levulinic acid and succinylacetone, and by chelating agents. PBGS behaved as a relatively heat-stable octameric complex of 292.3 kDa composed of 36.5 kDa subunits. Most general features of this insect PBGS were comparable to those published for other animal PBGS enzymes, while remarkable differences were found to the reported recombinant Drosophila enzyme. Moreover, rabbit antiserum directed against purified Pieris PBGS revealed significant immunological differences among insect PBGS enzymes from a wide range of orders contrasting to the overall evolutionary conserved features of this enzyme.

Rhodococcus erythropolis ATCC 25544 as a suitable source of cholesterol oxidase: cell-linked and extracellular enzyme synthesis, purification and concentration

BACKGROUND

The suitability of the strain Rhodococcus erythropolis ATCC 25544 grown in a two-liter fermentor as a source of cholesterol oxidase has been investigated. The strain produces both cell-linked and extracellular cholesterol oxidase in a high amount, that can be extracted, purified and concentrated by using the detergent Triton X-114.

RESULTS

A spray-dry method of preparation of the enzyme inducer cholesterol in Tween 20 was found to be superior in both convenience and enzyme synthesis yield to one of heat-mixing. Both were similar as far as biomass yield is concerned. Cell-linked cholesterol oxidase was extracted with Triton X-114, and this detergent was also used for purification and concentration, following temperature-induced detergent phase separation. Triton X-114 was utilized to purify and to concentrate the cell-linked and the extracellular enzyme. Cholesterol oxidase was found mainly in the resulting detergent-rich phase. When Triton X-114 concentration was set to 6% w/v the extracellular, but not the cell-extracted enzyme, underwent a 3.4-fold activation after the phase separation process. This result is interpreted in the light of interconvertible forms of the enzyme that do not seem to be in equilibrium. Fermentation yielded 360 U/ml (672 U/ml after activation), 36% of which was extracellular (65% after activation). The Triton X-114 phase separation step yielded 11.6-fold purification and 20.3-fold concentration.

CONCLUSIONS

The results of this work may make attractive and cost-effective the implementation of this bacterial strain and this detergent in a purification-based industrial production scheme of commercial cholesterol oxidase.

Purification of two calcium/calmodulin-dependent forms of cyclic nucleotide phosphodiesterase by using conformation-specific monoclonal antibody chromatography

A procedure for nondenaturing immunopurification of bovine calmodulin-dependent 3',5'-cyclic-nucleotide phosphodiesterase (3',5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17) is described that utilizes chromatography on a conformation-specific monoclonal antibody column. Hybridomas derived from spleen cells of mice immunized with Ca(2+)/calmodulin/phosphodiesterase were screened for antiphosphodiesterase antibody production. A stable cell line was established that secretes a monoclonal antibody that binds to the Ca(2+)/calmodulin/enzyme complex with an approximate K(d) of 10(-9) M. The dissociation constant was increased by two orders of magnitude when calmodulin interaction with the enzyme was inhibited by Ca(2+) chelation. This differential reactivity was utilized for affinity chromatography of heart and brain phosphodiesterases on monoclonal antibody columns. Highly purified phosphodiesterases were eluted in good yield with buffer containing EGTA. The immunopurified enzymes from heart and brain exhibited specific activities of approximately 300 units/mg when assayed at millimolar concentrations of cGMP or cAMP. Calmodulin stimulated both enzymes 10- to 15-fold over basal activity under these conditions. However, analysis of the two preparations by NaDodSO(4)/polyacrylamide gel electrophoresis revealed an apparent subunit of M(r) 61,000 for the brain enzyme, in contrast to the M(r) 59,000 cardiac subunit. The observed difference was not an artifact of tissue homogenization because both forms were detected after purification from mixed-tissue homogenates. These results suggest that mild, biospecific elution from a conformation-specific monoclonal antibody column may be a general technique applicable to the rapid isolation of proteins whose antigenic determinants can be altered with specific ligands.

Purification and separation of pyridine nucleotide-linked dehydrogenases by affinity chromatography techniques

A number of different dehydrogenases have been shown to bind to Sepharose-bound N(6)-(6-aminohexyl)-AMP. These dehydrogenases can be specifically eluted by binary adducts of NAD(+) or with cofactor gradients. In such manner pure enzymes can be obtained from crude extracts, as demonstrated in the purification on a preparative scale of lactate dehydrogenase from dogfish muscle. The data presented indicate the usefulness of general ligands as affinity agents. The techniques are particularly adaptable for the isolation of human mutant enzymes in blood or in the purification and concentration of enzymes present at low levels in fluids or tissues, as shown in the extensive purification of serum lactate dehydrogenase and glucose 6-phosphate dehydrogenase from hemolysate. lsoenzymes with different affinities for co-enzymes can be separated by affinity techniques. Application of affinity techniques may lead to the separation of isoenzymes or mutant enzymes that are not separable by electrophoretic methods.