Purification, Characterization and Antioxidant Potential of a Novel Lectin from Pterocarpus soyauxii Taub Seeds

The study investigated the presence of lectin in the seeds of Pterocarpus soyauxii, purified the lectin and determined its physicochemical properties as well as its antioxidant potential. Purification of P. soyauxii seeds lectin (PSSL) was accomplished by ammonium sulphate precipitation and gel filtration on Sephadex G-100, hemagglutination assay was by serial dilution and DPPH radical scavenging, metal chelating and lipid peroxidation inhibition assays were employed to evaluate its antioxidant potential. PSSL agglutinated erythrocytes from human blood group ABO, rabbit and rat. Trypsinization enhanced agglutination which was inhibited by galactose, lactose and arabinose. The lectin activity was independent of metal ion, thermal stable up to 60 °C and at pH range of 6 to 8. Gel filtration estimated molecular weight was 65 kDa and subunit molecular weight was 35 kDa. PSSL showed significant antioxidant activity. The lectin was able to scavenge DPPH radical, chelate iron metal and inhibit lipid peroxidation with IC50 of 0.14 ± 1.33 mg/ml, 3.40 ± 0.37 mg/ml and 0.50 ± 0.08 mg/ml respectively. The results indicate that PSSL might be applied as natural antioxidant for the development of drug and food products for the benefit of human health.

Purification and biochemical characterization of a β-cyanoalanine synthase expressed in germinating seeds of Sorghum bicolor (L.) moench

Background β-Cyanoalanine synthase plays essential roles in germinating seeds, such as in cyanide homeostasis. Methods β-Cyanoalanine synthase was isolated from sorghum seeds, purified using chromatographic techniques and its biochemical and catalytic properties were determined. Results The purified enzyme had a yield of 61.74% and specific activity of 577.50 nmol H2S/min/mg of protein. The apparent and subunit molecular weight for purified β-cyanoalanine synthase were 58.26±2.41 kDa and 63.4 kDa, respectively. The kinetic parameters with sodium cyanide as substrate were 0.67±0.08 mM, 17.60±0.50 nmol H2S/mL/min, 2.97×10−1 s−1 and 4.43×102 M−1 s−1 for KM, Vmax, kcat and kcat/KM, respectively. With L-cysteine as substrate, the kinetic parameters were 2.64±0.37 mM, 63.41±4.04 nmol H2S/mL/min, 10.71×10−1 s−1 and 4.06×102 M−1 s−1 for KM, Vmax, kcat and kcat/KM, respectively. The optimum temperature and pH for activity were 35°C and 8.5, respectively. The enzyme retained more than half of its activity at 40°C. Inhibitors such as HgCl2, EDTA, glycine and iodoacetamide reduced enzyme activity. Conclusion The biochemical properties of β-cyanoalanine synthase in germinating sorghum seeds highlights its roles in maintaining cyanide homeostasis.

Camphor Pathway Redux: Functional Recombinant Expression of 2,5- and 3,6-Diketocamphane Monooxygenases of Pseudomonas putida ATCC 17453 with Their Cognate Flavin Reductase Catalyzing Baeyer-Villiger Reactions

ABSTRACTWhereas the biochemical properties of the monooxygenase components that catalyze the oxidation of 2,5-diketocamphane and 3,6-diketocamphane (2,5-DKCMO and 3,6-DKCMO, respectively) in the initial catabolic steps of (+) and (−) isomeric forms of camphor (CAM) metabolism inPseudomonas putidaATCC 17453 are relatively well characterized, the actual identity of the flavin reductase (Fred) component that provides the reduced flavin to the oxygenases has hitherto been ill defined. In this study, a 37-kDa Fred was purified from a camphor-induced culture ofP. putidaATCC 17453 and this facilitated cloning and characterization of the requisite protein. The active Fred is a homodimer with a subunit molecular weight of 18,000 that uses NADH as an electron donor (Km= 32 μM), and it catalyzes the reduction of flavin mononucleotide (FMN) (Km= 3.6 μM;kcat= 283 s−1) in preference to flavin adenine dinucleotide (FAD) (Km= 19 μM;kcat= 128 s−1). Sequence determination of ∼40 kb of the CAM degradation plasmid revealed the locations of two isofunctional 2,5-DKCMO genes (camE25–1for 2,5-DKCMO-1 andcamE25–2for 2,5-DKCMO-2) as well as that of a 3,6-DKCMO-encoding gene (camE36). In addition, by pulsed-field gel electrophoresis, the CAM plasmid was established to be linear and ∼533 kb in length. To enable functional assessment of the two-component monooxygenase system in Baeyer-Villiger oxidations, recombinant plasmids expressing Fred in tandem with the respective 2,5-DKCMO- and 3,6-DKCMO-encoding genes inEscherichia coliwere constructed. Comparative substrate profiling of the isofunctional 2,5-DCKMOs did not yield obvious differences in Baeyer-Villiger biooxidations, but they are distinct from 3,6-DKCMO in the stereoselective oxygenations with various mono- and bicyclic ketone substrates.

Molecular cloning and characterization of glucose-6-phosphate dehydrogenase from Brugia malayi

SUMMARYGlucose-6-phosphate dehydrogenase (G6PD), a regulatory enzyme of the pentose phosphate pathway from Brugia malayi, was cloned, expressed and biochemically characterized. The Km values for glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (NADP) were 0·25 and 0·014 mm respectively. The rBmG6PD exhibited an optimum pH of 8·5 and temperature, 40 °C. Adenosine 5′ [γ-thio] triphosphate (ATP-γ-S), adenosine 5′ [β,γ-imido] triphosphate (ATP-β,γ-NH), adenosine 5′ [β-thio] diphosphate (ADP-β-S), Na+, K+, Li+ and Cu++ ions were found to be strong inhibitors of rBmG6PD. The rBmG6PD, a tetramer with subunit molecular weight of 75 kDa contains 0·02 mol of SH group per mol of monomer. Blocking the SH group with SH-inhibitors, led to activation of rBmG6PD activity by N-ethylmaleimide. CD analysis indicated that rBmG6PD is composed of 37% α-helices and 26% β-sheets. The unfolding equilibrium of rBmG6PD with GdmCl/urea showed the triphasic unfolding pattern along with the highly stable intermediate obtained by GdmCl.

Purification and characterization of phosphoenolpyruvate carboxykinase from Raillietina echinobothrida, a cestode parasite of the domestic fowl

SUMMARYPhosphoenolpyruvate carboxykinase (PEPCK, EC 4.1.1.32) is an essential regulatory enzyme of glycolysis in helminths in contrast to its role in gluconeogenesis in their host. Previously we have reported that phytochemicals from Flemingia vestita (Family: Fabaceae), genistein in particular, have vermifugal action and are known to affect carbohydrate metabolism in the cestode, Raillietina echinobothrida. In order to determine the functional differences of PEPCK from the parasite and its avian host (Gallus domesticus), we purified the parasite enzyme apparently to homogeneity, and characterized it. The native PEPCK is a monomer with a subunit molecular weight of 65 kDa. The purified enzyme displayed standard Michaelis-Menten kinetics with Km value of 42·52 μM for its substrate PEP. The Ki for the competitive inhibitors GTP, GMP, ITP and IMP for the carboxylation reaction were determined and discussed. In order to identify putative modulators from plant sources, phytochemicals from F. vestita and Stephania glabra were tested on the purified PEPCK, which resulted in alteration of its activity. From our results, we hypothesize that PEPCK may be a potential target site for anthelmintic action.

Purification and Characterization of TrzF: Biuret Hydrolysis by Allophanate Hydrolase Supports Growth

ABSTRACT TrzF, the allophanate hydrolase from Enterobacter cloacae strain 99, was cloned, overexpressed in the presence of a chaperone protein, and purified to homogeneity. Native TrzF had a subunit molecular weight of 65,401 and a subunit stoichiometry of α2 and did not contain significant levels of metals. TrzF showed time-dependent inhibition by phenyl phosphorodiamidate and is a member of the amidase signature protein family. TrzF was highly active in the hydrolysis of allophanate but was not active with urea, despite having been previously considered a urea amidolyase. TrzF showed lower activity with malonamate, malonamide, and biuret. The allophanate hydrolase from Pseudomonas sp. strain ADP, AtzF, was also shown to hydrolyze biuret slowly. Since biuret and allophanate are consecutive metabolites in cyanuric acid metabolism, the low level of biuret hydrolase activity can have physiological significance. A recombinant Escherichia coli strain containing atzD, encoding cyanuric acid hydrolase that produces biuret, and atzF grew slowly on cyanuric acid as a source of nitrogen. The amount of growth produced was consistent with the liberation of 3 mol of ammonia from cyanuric acid. In vitro, TrzF was shown to hydrolyze biuret to liberate 3 mol of ammonia. The biuret hydrolyzing activity of TrzF might also be physiologically relevant in native strains. E. cloacae strain 99 grows on cyanuric acid with a significant accumulation of biuret.

Characterization of Lacrimal Gland Carbonic Anhydrase VI

We have previously demonstrated by immunohistochemistry the presence of secreted carbonic anhydrase (CA VI) in the acinar cells of the rat lacrimal glands. In this study we purified the sheep lacrimal gland CA VI to homogeneity and demonstrated by Western analysis that it has the same apparent subunit molecular weight (45 kD) as the enzyme isolated from saliva. RT-PCR analysis showed that CA VI mRNA from the lacrimal gland was identical to that of the parotid gland CA VI mRNA. An RIA specific for sheep CA VI showed the lacrimal gland tissue concentration of the enzyme to be 4.20 ± 2.60 ng/mg protein, or about 1/7000 of the level found in the parotid gland. Immunohistochemistry (IHC) and in situ hybridization (ISH) showed that lacrimal acinar cells expressed both immunoreactivity and mRNA for CA VI. Moreover, CA VI immunoreactivity was occasionally observed in the lumen of the ducts. Unlike the parotid gland, in which all acinar cells expressed CA VI immunoreactivity and mRNA, only some of the acinar cells of the lacrimal gland showed expression. These results indicate that the lacrimal gland synthesizes and secretes a very small amount of salivary CA VI. In tear fluid, CA VI is presumed to have a role in the maintenance of acid/base balance on the surface of the eye, akin to its role in the oral cavity.

Glutamate dehydrogenase from liver of euthermic and hibernating Richardson's ground squirrels: Evidence for two distinct enzyme forms

Glutamate dehydrogenase (GDH) was purified to homogeneity from the liver of euthermic (37°C body temperature) and hibernating (torpid, 5°C body temperature) Richardson's ground squirrels (Spermophilus richardsonii). SDS-PAGE yielded a subunit molecular weight of 59.5 ± 2 kDa for both enzymes, but reverse phase and size exclusion HPLC showed native molecular weights of 335 ± 5 kDa for euthermic and 320 ± 5 kDa for hibernator GDH. Euthermic and hibernator GDH differed substantially in apparent Km values for glutamate, NH4+, and α-ketoglutarate, as well as in Ka and IC50 values for nucleotide and ion activators and inhibitors. Kinetic properties of each enzyme were differentially affected by assay temperature (37 versus 5°C). For example, the Km for α-ketoglutarate of euthermic GDH was higher at 5°C (3.66 ± 0.34 mM) than at 37°C (0.10 ± 0.01 mM), whereas hibernator GDH had a higher affinity for α-ketoglutarate at 5°C (Km was 0.98 ± 0.08 mM at 37°C and 0.43 ± 0.02 mM at 5°C). Temperature effects on Ka ADP values of the enzymes followed a similar pattern; GTP inhibition was strongest with the euthermic enzyme at 37°C and weakest with hibernator GDH at 5°C. Entry into hibernation leads to stable changes in the properties of ground squirrel liver GDH that allow the enzyme to function optimally at the prevailing body temperature.Key words: mammalian hibernation, amino acid metabolism, temperature-dependent enzyme kinetics, Spermophilus richardsonii.

An Unusual Oxygen-Sensitive, Iron- and Zinc-Containing Alcohol Dehydrogenase from the Hyperthermophilic Archaeon Pyrococcus furiosus

ABSTRACT Pyrococcus furiosus is a hyperthermophilic archaeon that grows optimally at 100°C by the fermentation of peptides and carbohydrates to produce acetate, CO2, and H2, together with minor amounts of ethanol. The organism also generates H2S in the presence of elemental sulfur (S0). Cell extracts contained NADP-dependent alcohol dehydrogenase activity (0.2 to 0.5 U/mg) with ethanol as the substrate, the specific activity of which was comparable in cells grown with and without S0. The enzyme was purified by multistep column chromatography. It has a subunit molecular weight of 48,000 ± 1,000, appears to be a homohexamer, and contains iron (∼1.0 g-atom/subunit) and zinc (∼1.0 g-atom/subunit) as determined by chemical analysis and plasma emission spectroscopy. Neither other metals nor acid-labile sulfur was detected. Analysis using electron paramagnetic resonance spectroscopy indicated that the iron was present as low-spin Fe(II). The enzyme is oxygen sensitive and has a half-life in air of about 1 h at 23°C. It is stable under anaerobic conditions even at high temperature, with half-lives at 85 and 95°C of 160 and 7 h, respectively. The optimum pH for ethanol oxidation was between 9.4 and 10.2 (at 80°C), and the apparent Km s (at 80°C) for ethanol, acetaldehyde, NADP, and NAD were 29.4, 0.17, 0.071, and 20 mM, respectively. P. furiosus alcohol dehydrogenase utilizes a range of alcohols and aldehydes, including ethanol, 2-phenylethanol, tryptophol, 1,3-propanediol, acetaldehyde, phenylacetaldehyde, and methyl glyoxal. Kinetic analyses indicated a marked preference for catalyzing aldehyde reduction with NADPH as the electron donor. Accordingly, the proposed physiological role of this unusual alcohol dehydrogenase is in the production of alcohols. This reaction simultaneously disposes of excess reducing equivalents and removes toxic aldehydes, both of which are products of fermentation.