Retention Modelling of Phenoxy Acid Herbicides in Reversed-Phase HPLC under Gradient Elution

Phenoxy acid herbicides are used worldwide and are potential contaminants of drinking water. Reversed phase high-performance liquid chromatography (RP-HPLC) is commonly used to monitor phenoxy acid herbicides in water samples. RP-HPLC retention of phenoxy acids is affected by both mobile phase composition and pH, but the synergic effect of these two factors, which is also dependent on the structure and pKa of solutes, cannot be easily predicted. In this paper, to support the setup of RP-HPLC analysis of phenoxy acids under application of linear mobile phase gradients we modelled the simultaneous effect of the molecular structure and the elution conditions (pH, initial acetonitrile content in the eluent and gradient slope) on the retention of the solutes. In particular, the chromatographic conditions and the molecular descriptors collected on the analyzed compounds were used to estimate the retention factor k by Partial Least Squares (PLS) regression. Eventually, a variable selection approach, Genetic Algorithms, was used to reduce the model complexity and allow an easier interpretation. The PLS model calibrated on the retention data of 15 solutes and successively tested on three external analytes provided satisfying and reliable results.

Electro Fenton removal of clopyralid in soil washing effluents

The removal of a commercial herbicide, based on clopyralid, by means of Electro-Fenton (EF) was studied using a soil washing effluent obtained using synthetic ground water as washing fluid. From the results, it was observed that the degradation and mineralization yields of clopyralid were high, even without the addition of supporting electrolyte. The groundwater could be then used as a sustainable supporting electrolyte. The influence of the minerals constituents, the current and the ferrous ions regeneration was evaluated. The highest hydrogen peroxide production was achieved working at 200 mA but regeneration of ferrous ions was not efficient at this current. Iodide ions were one of the main responsible in the EF efficiency decrease due to their reaction with the produced hydrogen peroxide. Electrochemical study proved that clopyralid was not electroactive and that its degradation was mainly due to radical oxidation. Long duration electrolysis carried out at 200 mA in groundwater provided an improvement of the solution biodegradability after 480 min that can be linked to a significant increase in the carboxylic acids production. These results support the feasibility of applying an EF process in order to carry out a subsequent biological mineralization.

Enhanced electrolytic treatment for the removal of clopyralid and lindane

In this work, it is evaluated the more critical point of a new electrochemical technology for the removal of organic pollutants based on the regeneration of granular active carbon (GAC) (that can be used efficiently to concentrate aqueous wastes) with methanol and in the electrochemical treatment of methanol with conductive diamond electrochemical oxidation (CDEO). The system proposed was studied with lindane and clopyralid. Results show that it is possible the complete removal of the raw pesticides and intermediates formed by electrolyzing these species in methanol media and that both sodium chloride and sodium hydroxide can be used as supporting electrolyte to increase the conductivity of methanol. The cell voltages obtained are quite similar to those obtained during the electrolysis of aqueous wastes. The electrolysis of these dilute solutions does not generate significant concentrations of intermediates and the depletion of the raw pollutant fits well to a pseudo-first order kinetic model. Oxidants capable to oxidize iodide to iodine are produced during the electrolysis in methanol media and they have an important influence on the degradation of the pollutants. The new technology, based on the concentration of the pollutant before electrolysis, allows to remove completely pollutants from soil and soil washing fluids in a more efficient way, although the concentration of pollutant attained and, hence, the efficiency of the overall removal process depends on the adsorption equilibria of the pollutant in aqueous and methanol media.

Hard coral (Porites lobata) extracts and homarine on cytochrome P450 expression in Hawaiian butterflyfishes with different feeding strategies

Dietary specialists tend to be less susceptible to the effects of chemical defenses produced by their prey compared to generalist predators that feed upon a broader range of prey species. While many researchers have investigated the ability of insects to detoxify dietary allelochemicals, little research has been conducted in marine ecosystems. We investigated metabolic detoxification pathways in three species of butterflyfishes: the hard coral specialist feeder, Chaetodon multicinctus, and two generalist feeders, Chaetodon auriga and Chaetodon kleinii. Each species was fed tissue homogenate of the hard coral Porites lobata or the feeding deterrent compound homarine (found in the coral extract), and the expression and catalytic activity of cytochrome P450 (CYP) 3A-like and CYP2-like enzymes were examined after one-week of treatment. The P. lobata homogenate significantly induced content and catalytic activity of CYP2-like and CYP3A-like forms, by 2-3 fold and by 3-9 fold, respectively, in C. multicinctus. Homarine caused a significant decrease of CYP2-like and CYP3A-like proteins at the high dose in C. kleinii and 60-80% mortality in that species. Homarine also induced CYP3A-like content by 3-fold and catalytic activity by 2-fold in C. auriga, while causing non-monotonic increases in CYP2-like and CYP3A-like catalytic activity in C. multicinctus. Our results indicate that dietary exposure to coral homogenates and the feeding deterrent constituent within these homogenates caused species-specific modulation of detoxification enzymes consistent with the prey selection strategies of generalist and specialist butterflyfishes.

Effect of solvents on the extraction of natural pigments and adsorption onto TiO2 for dye-sensitized solar cell applications

Nine solvents, namely, n-hexane, ethanol, acetonitrile, chloroform, ethyl-ether, ethyl-acetate, petroleum ether, n-butyl alcohol, and methanol were used to extract natural dyes from Cordyline fruticosa, Pandannus amaryllifolius and Hylocereus polyrhizus. To improve the adsorption of dyes onto the TiO2 particles, betalain and chlorophyll dyes were mixed with methanol or ethanol and water at various ratios. The adsorption of the dyes mixed with titanium dioxide (TiO2) was also observed. The highest adsorption of the C.fruticosa dye mixed with TiO2 was achieved at ratio 3:1 of methanol: water. The highest adsorption of P.amaryllifolius dye mixed with TiO2 was observed at 2:1 of ethanol: water. H.polyrhizus dye extracted by water and mixed with TiO2 demonstrated the highest adsorption among the solvents. All extracted dye was adsorbed onto the surface of TiO2 based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The inhibition of crystallinity of TiO2 was likewise investigated by X-ray analysis. The morphological properties and composition of dyes were analyzed via SEM and EDX.

Studies on Betaxanthin Profiles of Vegetables and Fruits from the Chenopodiaceae and Cactaceae

The present study provides an update on the betaxanthin (bx) compositions of red and yellow beetroots, yellow-coloured Swiss chard petioles, and yellow-orange cactus pear. Applying RP-HPLC coupled with positive ion electrospray mass spectrometry and by comparison with UV-vis and mass spectrometric characteristics as well as retention times of semisynthesized reference compounds, 24 betaxanthins were identified in red and yellow beetroot hypocotyls. Twenty-five and thirteen betaxanthins were present in yellow Swiss chard petioles and the cactus pear cultivar ‘Gialla’, respectively. Ethanolamine-bx and threonine-bx were found to be novel betaxanthins in Chenopodiaceae representatives, which to the best of our knowledge have not been reported as genuine pigments so far. Furthermore, aspartic acidbx (miraxanthin II), lysine-bx, and methionine-bx, hitherto found in other families, were identified in the Chenopodiaceae for the first time. Additionally, tyrosine-bx (portulacaxanthin II) and tryptophan-bx have not been earlier reported to occur in the Cactaceae. These findings provide valuable phytochemical information and may be useful for a better understanding of the functional properties of betaxanthins in plants.

Improved separation and detection of picolinic acid and quinolinic acid by capillary electrophoresis-mass spectrometry: application to analysis of human cerebrospinal fluid

"Quinolinic acid (QA)", a metabolite of the kynurenine pathway (KP), is implicated as a major neurological biomarker, which causes inflammatory disorders, whereas there is an increase evidence of the role of picolinic acid (PA) in neuroinflammation. Therefore, there is an urgent need to develop new clinical test for early diagnosis of neuroinflammatory disorders. A comparison is made between three different platforms such as high performance liquid chromatography-electrospray mass spectrometry (HPLC-ESI-MS/MS), nano LC-Chip/ESI-MS/MS, as well as the use of cationic (quaternary ammonium) and anionic (sulfonated) coated capillaries in capillary electrophoresis (CE)-ESI-MS/MS. The comparison revealed that CE-ESI-MS/MS method using a quaternary ammonium coated capillary is the best method for analysis of PA and QA. A simple stacking procedure by the inclusion of acetonitrile in the artificial cerebrospinal fluid (CSF) sample was employed to improve the peak shape and sensitivity of KP metabolites in CE-ESI-MS/MS. The developed CE-ESI-MS/MS assay provided high resolution, high specificity and high sensitivity with a total analysis time including sample preparation of nearly 12 min. In addition, excellent intra-day and inter-day repeatability of migration times and peak areas of the metabolites were observed with respective relative standard deviation (RSD) of less than 2.0% and 2.5%. Somewhat broader variations in repeatability for a 3 independently prepared coated capillary (total 35 runs each) with % RSD up to 3.8% and 5.8% was observed for migration time and peak areas, respectively. Artificial CSF was used as a surrogate matrix to simultaneously generate calibration curves over a concentration range of 0.02-10 μM for PA and 0.4-40 μM for QA. The method was then successfully applied to analyze PA and QA in human CSF, demonstrating the potential of this CE-ESI-MS/MS method to accurately quantitate with high specificity and sensitivity.

[Studies on the chemical constituents from aerial parts of Gynura divaricata]

OBJECTIVE

To study the chemical constituents from aerial parts of Gynura divaricata.

METHODS

The constituents were isolated on silica gel column chromatography, preparative TLC and Sephadex LH-20 column chromatography, identified by physicochemical properties and the structures were elucidated by spectral analysis.

RESULTS

10 compounds were isolated and identified as 2-(1', 2', 3', 4'-tetrahydroxybutyl)-6-(2", 3", 4"-trihydroxybutyl)-pyrazine (1), 2-(1', 2', 3', 4'-tetrahydroxybutyl)-5-(2", 3", 4"-trihydroxybutyl) -pyrazine (2), nicotinic acid (3), 5-hydroxy-picolinic acid(4), methyl-5-hydroxy-2- pyridinecarboxylate (5), adenosine (6), uridine (7), stigmasterol-5-O- beta-D-glucoside (8), dibutyl terephthalate (9), methyl chlorogenate (10).

CONCLUSION

Compounds 1, 2, 5, 9, 10 are obtained from this genus for the first time, Compounds 3, 4 are obtained from this plant for the first time.

Fluorescence detection of tyrosinase activity on dopamine-betaxanthin purified from Portulaca oleracea (common purslane) flowers

Tyrosinase or polyphenol oxidase (EC 1.14.18.1) is one of the key enzymes for the biosynthesis of natural pigment betalains. These are an important class of water-soluble pigments, characteristic of plants belonging to the order Caryophyllales. In this work, dopamine-betaxanthin (also known as miraxanthin V) is reported as the pigment responsible for the bright coloration in yellow flowers of Portulaca oleracea (common purslane). The natural pigment is purified, and used as a substrate for the catecholase (diphenolase) activity of the enzyme tyrosinase. A new, continuous method to follow the activity is developed based on the fluorescent properties of the betaxanthin. Fluorescence of the enzyme activity derived products is reported for the first time. Relevance of the fluorescent phenomenon is discussed based on fluorescence images and the description of a physiological inner filter effect present in flowers of P. oleracea. The first description of the betalain content in flower pistils is also provided.

Spore detection in aerobic granules by different dipicolinic acid releasing methods

This work aimed at developing a procedure for spore quantification. Spore content was determined by analyzing dipicolinic acid (dpa) extracted from aerobic granules by 13 methods. Concentrated HCl was able to release dpa completely. Results showed that dpa constituted 33.7 mg per g SS, meaning that about 337 mg per g SS were spores, not the normal vegetative cells.

Antimicrobial activity in the common seawhip, Leptogorgia virgulata (Cnidaria: Gorgonaceae)

Antimicrobial activity was examined in the gorgonian Leptogorgia virgulata (common seawhip) from South Carolina waters. Extraction and assay protocols were developed to identify antimicrobial activity in crude extracts of L. virgulata. Detection was determined by liquid growth inhibition assays using Escherichia coli BL21, Vibrio harveyii, Micrococcus luteus, and a Bacillus sp. isolate. This represents the first report of antimicrobial activity in L. virgulata, a temperate/sub-tropical coral of the western Atlantic Ocean. Results from growth inhibition assays guided a fractionation scheme to identify active compounds. Reverse-phase HPLC, HPLC-mass spectrometry, and 1H and 13C NMR spectroscopy were used to isolate, purify, and characterize metabolites in antimicrobial fractions of L. virgulata. Corroborative HPLC-MS/NMR evidence validated the presence of homarine and a homarine analog, well-known emetic metabolites previously isolated from L. virgulata, in coral extracts. In subsequent assays, partially-purified L. virgulata fractions collected from HPLC-MS fractionation were shown to contain antimicrobial activity using M. luteus and V. harveyii. This study provides evidence that homarine is an active constituent of the innate immune system in L. virgulata. We speculate it may act synergistically with cofactors and/or congeners in this octocoral to mount a response to microbial invasion and disease.

Floral fluorescence effect

The way flowers appear to insects is crucial for pollination. Here we describe an internal light-filtering effect in the flowers of Mirabilis jalapa, in which the visible fluorescence emitted by one pigment, a yellow betaxanthin, is absorbed by another, a violet betacyanin, to create a contrasting fluorescent pattern on the flower's petals. This finding opens up new possibilities for pollinator perception as fluorescence has not previously been considered as a potential signal in flowers.

A novel method using high-performance liquid chromatography with fluorescence detection for the determination of betaxanthins

Betaxanthins are natural water-soluble yellow pigments present in plants of the order Caryophyllales. The native fluorescence of these compounds is extensively characterized in this work, with study of the fluorescent properties of 14 different betaxanthins. All the species showed a similar behavior, with excitation maxima between 463 and 475 nm and emission maxima between 506 and 515 nm. Thus, betaxanthins absorb light corresponding to the blue color and emit visible green light. Similarities in excitation and emission spectra point to the responsibility of betalamic acid in fluorescence. The influence of the amine moiety is discussed. For the first time fluorescent properties of betaxanthins are applied to the detection of these pigments after separation by high-performance liquid chromatography. Wavelengths used were 460 nm for excitation and 510 nm for emission, which were suitable for detecting the native fluorescence of all the pigments assayed. Calibration was performed in each case and it exhibited linearity within the range considered, at least 20 microM. The lowest detection limit was 100 nM, corresponding to betaxanthins derived from methionine sulfoxide and leucine. Fluorescence detection was applied to the quantification of betaxanthins present in Carpobrotus acinaciformis. The present work opens up new possibilities for the analysis of betaxanthins by improving existing protocols through fluorescence detection.

Isolation of dipicolinic acid as an insecticidal toxin from Paecilomyces fumosoroseus

Several entomopathogenic fungi produce toxins that could be used as bioinsecticides in integrated pest management programs. Paecilomyces fumosoroseus is currently used for the biological control of the whiteflies Bemisia tabaci and B. argentifolii. Supernatants from submerged batch culture, where the fungus produced abundant dispersed mycelium, conidia and blastospores, were toxic to the whitefly nymphs. The most abundant metabolite was purified by HPLC and identified by mass spectrometry and NMR as dipicolinic acid. Both the dipicolinic acid produced by the fungus and the chemically synthesized compound had insecticidal activity against third-instar nymphs of the insect. Dipicolinic acid was toxic to the whitefly nymphs in bioassays involving topical applications. In submerged culture, the specific growth rate of P. fumosoroseus was 0.054 h-1, the specific glucose consumption rate was 0.1195 g g-1 h-1 and the specific dipicolinic acid production rate was 0.00012 g g-1 h-1. Dipicolinic acid was detected after 24 h when the fungus started growing; and dipicolinic acid production was directly correlated with fungal growth. Nevertheless, the yield was low and the maximal concentration was only 0.041 g l-1. The maximal concentrations of conidia and blastospores (per milliliter) were 1.4x10(8) and 7x10(7), respectively.

Mid-ultraviolet light-emitting diode detects dipicolinic acid

Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA (lambda(max) doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.

Stability of two new anticonvulsants in body fluids and tissues

Stability of two compounds with established anticonvulsant activity, picolinic acid benzylamide (Pic-BZA) and nicotinic acid benzylamide (Nic-BZA), incubated in homogenates of body organs and in body fluids was determined at different time points. Pic-BZA was found to decompose fairly rapidly in the liver and the kidney, while Nic-BZA demonstrated stability against enzymes present in these organs and fluids.

Novel cytokine production inhibitors produced by a basidiomycete, Marasmiellus sp

New cytokine production inhibitors, CJ-14,877 (I) and CJ-14,897 (II), were isolated from the fermentation broth of a basidiomycete, Marasmiellus sp. CL21624. Their structures were determined to be methyl-(7S,8S)-5-(7,8-dihydroxypropyl)pyridine-2-carboxylate and methyl-(7S,8S)-5-(8-acetoxy-7-hydroxypropyl)pyridine-2-carboxylate [corrected], respectively, by spectroscopic analyses. These compounds showed inhibitory activities for lipopolysaccharide-induced production of interleukin-1beta and tumor necrosis factor-alpha in human whole blood with IC50 values of the range from 0.059 to 2.6 microM.

Vertilecanins: new phenopicolinic acid analogues from Verticillium lecanii

Five new phenopicolinic acid analogues (1-5) have been isolated from solid-substrate fermentation cultures of Verticillium lecanii. The most abundant component (vertilecanin A; 1) displays antiinsectan activity against Helicoverpa zea. These compounds were obtained by chromatographic fractionation of the EtOAc culture extract and identified by analysis of NMR and MS data. The known fungal metabolites 2-decenedioic acid and 10-hydroxy-8-decenoic acid were also isolated from these cultures.

Halopicolinic acids, novel products arising through the degradation of chloro- and bromo-biphenyl by Sphingomonas paucimobilis BPSI-3

Sphingomonas paucimobilis BPSI-3 was previously isolated from a mixed microbial consortium growing on biphenyl as the sole source of carbon and energy. Transformation of 4-chlorobiphenyl (4CBP) was demonstrated by this strain, although little or no growth was observed. In minimal salts medium supplemented with 4CBP or bromobiphenyl and dextrose, yellow coloured product(s) were rapidly formed. Gas chromatography-mass spectrometry (GC-MS) revealed single-ring N-heterocyclic compounds that were identified as halopicolinic acids. We believe this to be the first report of such compounds being formed via biological transformation of halobiphenyls. A mechanism is proposed for their formation.

Isolation and characterization of two new fusaric acid analogs from Fusarium moniliforme NRRL 13,163

Fusarium moniliforme NRRL 13,163 produced two new fusaric acid analogs, a 10,11-dihydroxyfusaric acid and a diacid of fusaric acid in which the C-11 methyl was oxidized to a carboxyl. Several hundred milligrams of the 10,11-dihydroxyfusaric acid were routinely recovered from a kilogram of corn grit medium. It crystallized as white, irregularly shaped rectangles that melted at 153 to 154 degrees C. The diacid analog of fusaric acid crystallized as white rods that melted at 210 to 211 degrees C. Unlike the consistent recovery experienced with the 10,11-dihydroxyfusaric acid, the diacid analog proved difficult to purify after the initial discovery and was detectable in subsequent fermentations only by mass spectrometry.

Determination of dipicolinic acid in bacterial spores by derivative spectroscopy

Dipicolinic acid was extracted from approximately 0.1 mg spores or 0.5 ml of sporulating culture with 20 mM HCl for 10 min at 100 degrees C. The suspension was diluted with 5 mM Ca2+, 100 mM Tris, pH 7.6, centrifuged, and the first derivative of the uv absorbance spectrum recorded from 275 nm to 285 nm. DPA concentration was determined from the difference between the maximum at 276.6 nm and the minimum at 280 nm. The use of the difference between two first derivative values removed possible interference from sloping baselines. Turbidity, nucleic acids, and bacteriological media did not interfere. Analysis time for four extracts was 4 min using a spectrophotometer reading at 0.1-nm intervals. Dipicolinate at 0.1 mM gave 0.184 absorbance/nm at 25 degrees C. The coefficient of variation was 1.5%, and the detection limit 1 microM.

Characterization and quantitation of a zinc-binding ligand in human milk

A low-molecular-weight zinc-binding ligand from human milk has been isolated and characterized. The ligand was isolated by chromatography on Dowex 50, Dowex 1, and Sephadex G-15 equilibrated with 0.153 mM Zn(NO3)2. Mass spectroscopy, thin-layer chromatography, and infrared spectroscopy proved that the zinc-binding ligand isolated by this method from human milk is pyridine-2-carboxylic acid, commonly known as picolinic acid. The concentration of picolinic acid in human milk was 308 microM, the concentration in one brand of processed cow's milk was 20 microM, but picolinic acid was undetectable in a second brand of cow's milk and in four different infant formulas. Weanling rats fed supplemental picolinic acid absorbed significantly more dietary zinc and gained significantly more weight than rats fed an unsupplemented diet. The results suggest that the high bioavailability of zinc in human milk results from the presence of picolinic acid, a bidentate chelating ligand which facilitates zinc absorption from the intestine.

Experiments in marine biochemistry. Homarine metabolism in Penaeus duorarum

A fractionation procedure has been developed which permits the isolation of 1 to 2 mg of homarine from a single shrimp. This procedure was used to show that homarine is endogenously synthesized by Penaeus duorarum in the free unbound form, and to study the metabolic precursors involved. Injected DL-[14C]tryptophan was not converted to [14C]homarine. However, [6-14C]quinolinic acid, a known catabolite of tryptophan, is an effective precursor. [2-14C]Acetate and [U-14C]glycerol are effectively converted to [14C]homarine while [14C]bicarbonate is poorly utilized. The injection of L-[U-14C]aspartate resulted in labeled homarine, but the quantity converted was less than expected. Since [14C]glycerol is an effective precursor there is a possibility that quinolinic acid may be formed in P. duorarum by a condensation similar to that of glyceraldehyde 3-phosphate with aspartic acid or a closely related metabolite. It is suggested that decarboxylation of quinolinic acid gives rise to picolinic acid which is methylated to yield homarine. L-[methyl-14C]Methionine efficiently provides the N-methyl carbon presumably via S-adenosylmethionine.

Use of ultraviolet radiation to locate dipicolinic acid in Bacillus cereus spores

A novel method is described that allows a direct determination of the location of a portion of the dipicolinic acid (DPA) in spores. Ultraviolet (UV) irradiation is shown to cause cross-linkage of DPA to spore proteins which have the characteristics of membrane proteins. We suggest that DPA resides in the inner forespore membrane (IFSM) and spore cytoplasm (i.e., the spore protoplast). Only that portion of the DPA in the vicinity of the IFSM appeared to form UV-induced DPA-protein adducts.

Accumulation of dehydrofusaric acid and its conversion to fusaric and 10-hydroxyfusaric acids in cultures of Gibberella fujikuroi

Gibberella fujikuroi (Saw.) Wr. strain 917 produced dehydrofusaric acid in high yield when cultured in a defined medium containing adequate nitrogen. The metabolite was separated by partition chromatography from the small amount of fusaric acid present. Fusaric and dehydrofusaric acids can be interconverted by the culture since radioactivity administered as either 14C-labeled fusaric acid or 14C-labeled dehydrofusaric acid was distributed into both metabolites. Radioactivity also accumulated in more polar substances. These were isolated from cultures administered acetate-2-14C and the main radioactive product was identified as 10-hydroxyfusaric acid. 11-Chloro-10-hydroxyfusaric acid was tentatively identified in the culture extract, but may be an artifact.

Partial purification and characterization of dihydrodipicolinic acid synthetase from sporulating Bacillus megaterium

Sporulation of Bacillus megaterium Km (ATCC 13632) was synchronized by a technique employing three 10% transfers. The culture was harvested when 60% of the cells contained spore forms. Dihydrodipicolinic acid synthetase was purified 150-fold by ammonium sulfate fractionation at pH 6.5, heating for 15 min at 45 C at pH 6.0, ammonium sulfate fractionation at pH 6.0, and subsequent chromatography on diethylaminoethyl cellulose. During the final stage of the purification procedure, the enzyme exhibited sensitivity to refrigeration temperatures. The enzyme had a pH optimum of 7.65 in imidazole buffer. The apparent K(m) values were 4.6 x 10(-4) and 5.0 x 10(-4)m for beta-aspartyl semialdehyde and pyruvate, respectively. All attempts to demonstrate cofactor requirements were unsuccessful. Sulfhydryl inhibiting reagents and lysine did not inhibit the enzymatic reaction. The enzyme exhibited maximal thermal resistance at pH 10.5. The thermal stability of the enzyme at 75 C was increased more than 1,800-fold by the addition of 0.3 m pyruvate. The E(a) was 67,300 cal/mole for the thermal denaturation of the enzyme. At 60 C, the DeltaF, DeltaH, and DeltaS values for the thermal denaturation of the enzyme were 22,250, 66,700, and 133 cal per mole per degree, respectively.