Alcohol oxidase from Candida boidinii

Alcohol Oxidase from the Methylotrophic Yeast Ogataea polymorpha: Isolation, Purification, and Bioanalytical Application

Alcohol oxidase (EC 1.1.3.13; AOX) is a flavoprotein that catalyzes the oxidation of primary short-chain alcohols to corresponding carbonyl compounds with a concomitant release of hydrogen peroxide. It is a key enzyme of methanol metabolism in methylotrophic yeasts, catalyzing the first step of methanol oxidation to formaldehyde.Here we describe the isolation and purification of AOX from the thermotolerant methylotrophic yeast Ogataea (Hansenula) polymorpha, and using this enzyme in enzymatic assay of ethanol, simultaneous analysis of methanol and formaldehyde, and in construction of amperometric biosensors selective to primary alcohols and formaldehyde.

Purification and Characterization of Isoamyl Alcohol Oxidase ("Mureka"-Forming Enzyme)

Isoamyl alcohol oxidase (IAAOD) was purified to apparent homogeneity on SDS-PAGE from ultrafiltration (UF) concentrated sake. IAAOD was a glycoprotein, a monomeric protein with an apparent molecular mass of 73 and 87 kDa, by SDS-PAGE and gel filtration on HPLC, respectively. IAAOD showed high substrate specificity toward C5 branched-chain alkyl alcohol (isoamyl alcohol), and no activity toward shorter (C1-C4) or longer (C7-C10) alkyl alcohols tested. IAAOD was stable between pH 3.0-6.0 at 25°C. The optimum pH was 4.5 at 35°C. Heavy metal ions, p-chloromercuribenzoate (PCMB), hydrazine, and hydroxylamine strongly inhibited the enzyme activity, and an anti-oxidant like L-ascorbate did also. Isovaleraldehyde was produced markedly in pasteurized sake by adding purified IAAOD, therefore, we concluded that it was the enzyme that causes formation of mureka, an off-flavor of sake, the main component of which is isovaleraldehyde.

A comparative study of graphene-hydrogel hybrid bionanocomposites for biosensing

Hydrogels have become increasingly popular as immobilization materials for cells, enzymes and proteins for biosensing applications. Enzymatic biosensors that utilize hydrogel as an encapsulant have shown improvements over other immobilization techniques such as cross linking and covalent bonding. However, to date there are no studies which directly compare multiple hydrogel-graphene nanocomposites using the same enzyme and test conditions. This study compares the performance of four different hydrogels used as protein encapsulants in a mediator-free biosensor based on graphene-nanometal-enzyme composites. Alcohol oxidase (AOx) was encapsulated in chitosan poly-N-isopropylacrylamide (PNIPAAM), silk fibroin or cellulose nanocrystals (CNC) hydrogels, and then spin coated onto a nanoplatinum-graphene modified electrode. The transduction mechanism for the biosensor was based on AOx-catalyzed oxidation of methanol to produce hydrogen peroxide. To isolate the effect(s) of stimulus response on biosensor behavior, all experiments were conducted at 25 °C and pH 7.10. Electroactive surface area (ESA), electrochemical impedance spectroscopy (EIS), sensitivity to methanol, response time, limit of detection, and shelf life were measured for each bionanocomposite. Chitosan and PNIPAAM had the highest sensitivity (0.46 ± 0.2 and 0.3 ± 0.1 μA mM(-1), respectively) and electroactive surface area (0.2 ± 0.06 and 0.2 ± 0.02 cm(2), respectively), as well as the fastest response time (4.3 ± 0.8 and 4.8 ± 1.1 s, respectively). Silk and CNC demonstrated lower sensitivity (0.09 ± 0.02 and 0.15 ± 0.03 μA mM(-1), respectively), lower electroactive surface area (0.12 ± 0.02 and 0.09 ± 0.03 cm(2), respectively), and longer response time (8.9 ± 2.1 and 6.3 ± 0.8 s, respectively). The high porosity of chitosan, PNIPAAM, and silk gels led to excellent transport, which was significantly better than CNC bionanocomposites. Electrochemical performance of CNC bionanocomposites were relatively poor, which may be linked to poor gel stability. The differences between the Chitosan/PNIPAAM group and the Silk/CNC group were statistically significant (p < 0.05) based on ANOVA. Each of these composites was within the range of other published devices in the literature, while some attributes were significantly improved (namely response time and shelf life). The main advantages of these hydrogel composites over other devices is that only one enzyme is required, all materials are non-toxic, the sensor does not require mediators/cofactors, and the shelf life and response time are significantly improved over other devices.

Influence of phosphate and phosphoesters on the decomposition pathway of 1,2-bis(methylsulfonyl)-1-(2-chloroethyhydrazine (90CE), the active anticancer moiety generated by Laromustine, KS119, and KS119W

Prodrugs of the short-lived chloroethylating agent 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine (90CE) and its methylating analogue 1,2-bis(methylsulfonyl)-1-(methyl)hydrazine (KS90) are potentially useful anticancer agents. This class of agents frequently yields higher ratios of therapeutically active oxophilic electrophiles responsible for DNA O⁶-guanine alkylations to other electrophiles with lower therapeutic relevance than the nitrosoureas. This results in improved selectivity toward tumors with diminished levels of O⁶-alkylguanine-DNA alkyltransferase (MGMT), the resistance protein responsible for O⁶-alkylguanine repair. The formation of O⁶-(2-chloroethyl)guanine, which leads to the formation of a DNA–DNA interstrand cross-link, accounts for the bulk of the anticancer activity of 90CE prodrugs. Herein, we describe a new decomposition pathway that is available to 90CE but not to its methylating counterpart. This pathway appears to be subject to general/acid base catalysis with phosphate (Pi), phosphomonoesters, and phosphodiesters, being particularly effective. This pathway does not yield a chloroethylating species and results in a major change in nucleophile preference since thiophilic rather than oxophilic electrophiles are produced. Thus, a Pi concentration dependent decrease in DNA–DNA interstand cross-link formation was observed. Changes in 90CE decomposition products but not alkylation kinetics occurred in the presence of Pi since the prebranch point elimination of the N-1 methanesulfinate moiety remained the rate-limiting step. The Pi catalyzed route is expected to dominate at Pi and phosphoester concentrations totaling >25–35 mM. In view of the abundance of Pi and phosphoesters in cells, this pathway may have important effects on agent toxicity, tumor selectivity, and resistance to prodrugs of 90CE. Furthermore, it may be possible to design analogues that diminish this thiophile-generating pathway, which is likely superfluous at best and potentially detrimental to the targeting of hypoxic regions where Pi concentrations can be significantly elevated.

Chloroethylating and methylating dual function antineoplastic agents display superior cytotoxicity against repair proficient tumor cells

Two new agents based upon the structure of the clinically active prodrug laromustine were synthesized. These agents, 2-(2-chloroethyl)-N-methyl-1,2-bis(methylsulfonyl)-N-nitrosohydrazinecarboxamide (1) and N-(2-chloroethyl)-2-methyl-1,2-bis(methylsulfonyl)-N-nitrosohydrazinecarboxamide (2), were designed to retain the potent chloroethylating and DNA cross-linking functions of laromustine, and gain the ability to methylate DNA at the O-6 position of guanine, while lacking the carbamoylating activity of laromustine. The methylating arm was introduced with the intent of depleting the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT). Compound 1 is markedly more cytotoxic than laromustine in both AGT minus EMT6 mouse mammary carcinoma cells and high AGT expressing DU145 human prostate carcinoma cells. DNA cross-linking studies indicated that its cross-linking efficiency is nearly identical to its predicted active decomposition product, 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine (90CE), which is also produced by laromustine. AGT ablation studies in DU145 cells demonstrated that 1 can efficiently deplete AGT. Studies assaying methanol and 2-chloroethanol production as a consequence of the methylation and chloroethylation of water by 1 and 2 confirmed their ability to function as methylating and chloroethylating agents and provided insights into the superior activity of 1.

A sensitive method for rapid detection of alkyl halides and dehalogenase activity using a multistep enzyme assay

A method for the detection of haloalkane conversion to the corresponding alcohols by haloalkane dehalogenases is described. It is based on a multistage enzyme reaction which allows for the analysis of alkyl halides in buffered systems. Irreversible hydrolytic dehalogenation catalyzed by haloalkane dehalogenase DhaA from Rhodococcus erythropolis transfers an alkyl halide into a corresponding alcohol that is further oxidized by alcohol oxidase AOX from Pichia pastoris yielding a respective aldehyde and hydrogen peroxide easily detectable via the horseradish peroxidase catalyzed oxidation of chromogenic molecules. Due to its high sensitivity (0.025 mM, 0.43 ppm for 1,3-dibromopropane), low expenditure and the ability of handling a large number of samples in parallel, this method is an attractive alternative to existing procedures for the monitoring of both haloalkanes and dehalogenases.

Purification and characterization of intracellular and extracellular, thermostable and alkali-tolerant alcohol oxidases produced by a thermophilic fungus, Thermoascus aurantiacus NBRC 31693

Intracellular and extracellular alcohol oxidases (AO int and AO ext) were purified from the liquid and solid cultures of a thermophilic fungus, Thermoascus aurantiacus NBRC 31693, as electrophoretically and isoelectrophoretically homogeneous proteins, respectively. Both enzymes contained a flavin adenine dinucleotide (FAD) cofactor and were stained with Schiff's reagent. The molecular weight of AO int was estimated to be about 320 kDa and its subunit was 75 kDa. The molecular weight of AO ext was about 560 kDa, and it was composed of two types of subunits (75 kDa and 59 kDa). The pIs of AO int and AO ext were 5.88 and 6.08, respectively. AO int and AO ext were stable up to 60 degrees C and 55 degrees C, respectively. The enzymes were stable over a wide range of pH from 6 to 11. AO int oxidized short straight-chain alcohols (K(m) for methanol, 13.5 mM and K(m) for ethanol, 15.8 mM). On the other hand, AO ext could oxidize secondary alcohols and aromatic alcohols (veratryl alcohol and benzyl alcohol) in addition to straight-chain alcohols (K(m) for methanol, 0.5 mM and K(m) for ethanol, 10.2 mM).

Copper adaptation and methylotrophic metabolism in Candida boidinii

The importance of the antioxidant enzyme superoxide dismutase (CuZnSOD) in the metabolic switch from normotrophic to methylotrophic conditions was studied in the facultative methylotrophic yeast Candida boidinii. Copper adaptation was performed to qualify C. boidinii as a suitable cellular system to study the effect of induction of CuZnSOD, and other biochemical components along the copper detoxification system, on methanol adaptation. Copper adaptation results in the induction of CuZnSOD peroxidase activity as well as of glutathione. The effects at the metabolic level of exposure to both copper and methanol were also studied: the results suggest that the effect on antioxidant enzyme levels as a function of the change of trophic condition are predominant with respect to the effects of copper administration. Thus, the methanol-dependent induction of such enzymes is likely to provide a sufficient protection for the cells against toxic effects depending on copper administration. Administration of copper under methylotrophic conditions decreases the growth rate in spite of the high levels of antioxidant enzymes that are elicited by copper treatment. The adaptation to methanol metabolism was studied alsoafter methanol-independent induction of CuZnSOD, glutathione and catalase levels, obtained by exposure to high copper concentrations in glucose-containing medium. The metabolic changes induced by copper are persistent over several re-inoculations in normo-cupric glucose medium, thus allowing the study of the glucose-to-methanol switch on cells exhibiting high levels of antioxidant enzyme activities. Under such conditions the lag time observed during the transition from normotrophic to methylotrophic conditions is strongly reduced.

A consensus sequence for long-chain fatty-acid alcohol oxidases from Candida identifies a family of genes involved in lipid omega-oxidation in yeast with homologues in plants and bacteria

The yeast Candida cloacae is capable of growing on alkanes and fatty acids as sole carbon sources. Transfer of cultures from a glucose medium to one containing oleic acid induced seven proteins of M(r) 102,000, 73,000, 61,000, 54,000, and 46,000 and two in the region of M(r) 45,000 and repressed a protein of M(r) 64,000. The induction of the M(r) 73,000 protein reached a 7-fold maximum 24 h after induction. The protein was confirmed by its enzyme activity to be a long-chain fatty-acid alcohol oxidase (LC-FAO) and purified to homogeneity from microsomes by a rapid procedure involving hydrophobic chromatography. An internal peptide of 30 amino acids was sequenced. A 1100-base pair cDNA fragment containing the LC-FAO peptide coding sequence was used to isolate a single exon genomic clone containing the full-length coding sequence of an LC-FAO (fao1). The fao1 gene product was expressed in Escherichia coli and was translated as a functional long-chain alcohol oxidase, which was present in the membrane fraction. In addition, full-length coding sequences for a Candida tropicalis LC-FAO (faoT) and a second C. cloacae LC-FAO (fao2) were isolated. The DNA sequences obtained had open reading frames of 2094 (fao1), 2091 (fao2), and 2112 (faoT) base pairs. The derived amino acid sequences of fao2 and faoT showed 89.4 and 76.2% similarities to fao1. The fao1 gene is much more highly induced on alkane than is fao2. Although this study describes the first known DNA sequences encoding LC-FAOs from any source, there are unassigned Arabidopsis sequences and an unassigned Mycobacterium sequence in the GenBank(TM) Data Bank that show strong homology to the described LC-FAO sequences. The conservation of sequence between yeast, plants, and bacteria suggests that an as yet undescribed family of long-chain fatty-acid oxidases exists in both eukaryotes and prokaryotes.

Superoxide dismutase, catalase and cell dimorphism in Candida albicans cells exposed to methanol and different temperatures

The combined effects of methanol and different temperatures on Candida albicans were studied. Growth curve, cell morphology, superoxide dismutase (SOD) and catalase activity levels have been determined. Cell growth in each medium was comparable to 28 degrees C and 37 degrees C. The growth rate was not affected by methanol, in the presence of glucose, while it was much lower in the absence of sugar. Cell dimorphism appeared after thermic stress and it was also dependent on the medium composition. In all media, both SOD and catalase levels were much higher at 37 degrees C. The presence of methanol per se did not affect the enzymatic levels, while the absence of glucose gave higher SOD levels.

Interaction among heavy metals and methanol affecting superoxide dismutase activity in Saccharomyces cerevisiae

1. Three strains of Saccharomyces cerevisiae have been exposed to methanol both in the presence and absence of heavy metal ions. The growth curves and the superoxide dismutase activity were determined. 2. The presence of alcohol, copper or cadmium alone did not give strong cytotoxic effects, while methanol plus cadmium yielded a growth inhibition in two strains. 3. SOD levels were stimulated by copper, while methanol did not affect SOD in this non-methylotrophic yeast, indicating the need of alcohol assimilation to stimulate SOD. Cadmium had no inducing effects on SOD levels.

Purification of the glycoprotein glucose oxidase from Penicillium amagasakiense by high-performance liquid chromatography

Fast protein liquid chromatography (FPLC) in combination with ion-exchange chromatography on a Mono Q column was used to purify glucose oxidase from Penicillium amagasakiense to homogeneity. Purification was performed with a mixed pH and salt gradient, with 20 mM phosphate buffer (pH 8.5) as starting buffer (A) and 50 mM acetate buffer (pH 3.6) with 0.1 M NaCl as elution buffer (B). Elution conditions were optimized to permit the simultaneous purification and separation of the glucose oxidase isoforms. Three peaks, each consisting of 1-2 isoforms and exhibiting a homogeneous titration curve profile, were resolved with a very flat linear gradient of 5.0-5.1% B in 40 ml. Three more peaks, each consisting of several isoforms, were eluted at 10%, 30% and 100% B. Optimization of the elution conditions and separation of the glucose oxidase isoforms was only possible because of the rapidity of each purification step and the high resolution provided by FPLC and Mono Q.

Separation of enzymes from Candida boidinii crude extract by continuous flow zone electrophoresis

Separation of the enzymes formate dehydrogenase, formaldehyde dehydrogenase and methanol oxidase from Candida boidinii crude extract has been explored using continuous flow zone electrophoresis in the VaP-22 and the scaled-up VaP-220 electrophoresis apparatus. Yields up to 95% and purification factors between 3 and 7 were obtained, together with separation of cell debris from the enzymes. Multiple injections of sample were used to obtain a protein throughput of 46.2 mg/h in the VaP-22. A tenfold higher throughput was achieved using the VaP-220. Correlation of the electrophoretic mobility in continuous flow zone electrophoresis with the elution behavior in ion-exchange chromatography confirmed the primary role of net surface charge in the separation of biological molecules. Proteins and enzymes with differences greater than 0.05 M elution molarities in ion-exchange chromatography can be separated. This corresponds to a preparative scale (mg/h or g/h) separation of proteins and enzymes whose difference in apparent electrophoretic mobility is greater than 0.70 x 10(-5) cm2/(V.s).