Changes in carotenoid and chlorophyll content of black tomatoes (Lycopersicone sculentum L.) during storage at various temperatures

Black tomatoes have a unique color and higher lycopene content than typical red tomatoes. Here, black tomatoes were investigated how maturation stage and storage temperature affected carotenoid and chlorophyll accumulation. Immature fruits were firmer than mature fruits, but failed to develop their distinctive color and contained less lycopene when stored at 8 °C. Hunter a^* values of black tomatoes increased with storage temperature and duration; storage of immature fruits at high temperature favored lycopene accumulation. Chlorophyll levels of black tomatoes declined during storage, but differences between mature and immature tomatoes stored at 12 °C were minimal. β-Carotene levels of black tomatoes increased during early storage, but rapidly declined beginning 13 d post-harvest. The highest lycopene and chlorophyll levels were observed in mature black tomatoes stored at 12 °C for 13 d; these conditions also yielded the best quality fruit. Thus, the unique pigmentation properties of black tomatoes can be precisely controlled by standardizing storage conditions.     

Effect of temperature and ripening stages on membrane integrity of fresh-cut tomatoes

The shelf-life of fresh-cut tomatoes mainly depends on loss of tissue integrity and firmness that occurs also in intact fruits after long-term cold storage due to chilling injury. Round-fruit tomatoes (Solanum lycopersicum L.) cv. Jama were stored in 1.1-L plastic (polyethylene) fresh-cut produce containers as 10.0-mm-thick tomato slices and as intact tomatoes at 4 ± 0.5 °C. The aim of this work was to study the loss of membrane integrity and biochemical processes involved in membrane disruption. Electrolyte leakage and lipid peroxidation were studied at different stages of maturity: mature green, pink (PK), fully ripe and two different storage temperatures: 4 and 15 °C. The tomato slices of PK stage stored at 4 °C did not show changes for both parameters, while significant increase in membrane leakage and lipid peroxidation was observed at 15 °C, especially after 24 h of storage. The enzymes showed a simultaneous increase in their activities with a rise in electrolyte leakage and lipid peroxidation after 7 days of storage. Finally, phospholipase C (PLC) and phospholipase D (PLD) were investigated for intact fruit and tomato slices stored at 4 °C. The PLC had higher activity compared with PLD. In conclusion, the loss of membrane integrity in fresh-cut tomatoes is mainly affected by ripening stages, storage temperature and duration. The wounds enhance the PLC and PLD activities and they play a role late during storage.     

Enzymatic antioxidant response to low-temperature acclimation in the cyanobacterium <Emphasis Type="Italic">Arthrospira platensis</Emphasis>

Changes in antioxidant enzyme activities in response to low-temperature-induced photoinhibition were investigated in the two strains of the cyanobacterium Arthrospira platensis, Kenya and M2. When transferred to 15°C from 33°C, cells exhibited an immediate cessation of growth followed by a new acclimated growth rate. Although both strains had similar growth rates at 33°C, once transferred to a lower temperature environment, Kenya had a faster growth rate than M2. There were variations in the antioxidant enzyme activities of both strains during 15°C acclimation. The activity of superoxide dismutase from Kenya was higher than that from M2 and increased remarkably with acclimation time. Catalase activity of both strains increased at first but decreased later in the acclimation process. Ascorbate-dependent peroxidase activity of the Kenya strain declined when transferred to the low-temperature environment while peroxidase activity of M2 decreased in the beginning and then increased with time. The dehydroascorbate reductase activity of both strains was variable during the acclimation period while the glutathione reductase activity was not modified immediately. Our finding may support that the faster growth rate of the Kenya strain at lower temperatures as compared with the M2 strain might be explained by the higher antioxidant enzyme activities of Kenya at lower temperatures and through its ability to apply a more efficient regulatory strategy of enzymatic antioxidant response to low-temperature-induced photoinhibition.     

Effects of hot water treatments and storage temperatures on the ripening and the use of electrical impedance as an index for assessing post-harvest changes in mango fruits

The effects of hot water treatment and storage temperature (4°C, 13°C or 22°C) on the quality and impedance of outer and inner mesocarp of mango were assessed in two experiments during storage, impedance being a potential non‐destructive measure of tissue damage following heat treatment. Fruits were subjected to equivalent heat units at 36.5°C for 60 min plus 46.5°C for 43 min or 46.5°C for 90 min by hot water treatments (hwt) on the assumption of cumulative heat effects and a base temperature of 12–13°C. Fruit reflectance decreased whereas chroma and hue angle increased over storage time and also with increase in storage temperature. The yellow colour increased with a rise in storage temperature in hot water treated mangoes. Soluble solids content of mangoes held at 22°C was highest at 5 days of storage but decreased subsequently over storage time. Impedance of all fruits decreased with increase in frequency, storage temperature and time in store. The impedance of hwt mangoes was lower than that of non‐hwt fruits 8 h after immersion, but recovered almost to control levels on day 5 at 4°C or 13°C, but decreased gradually after 5 days at 13°C. Impedance of all mangoes stored at 22°C decreased continuously during storage. Impedance was higher in the inner mesocarp than outer pulp. Impedance of hwt fruits was poorly correlated with soluble solid content and chroma but well correlated with reflectance of fruit pulp at 22°C. Changes in impedance of mangoes are discussed in relation to physiological and biochemical changes that occur during heat treatment and storage.     

Changes in the activity of enzymes of phenylpropanoid metabolism in tomatoes stored at low temperatures

A large increase in the activity of an enzyme involved in chlorogenic acid metabolism, hydroxycinnamyltransferase occurs in tomatoes stored at low temperatures. In contrast, the activity of the enzyme remains constant or falls slightly during normal ripening at 20°. The rise in activity occurs at temperatures below 10° and fails to occur at 15° or 20°. This increase in activity during low temperature storage occurs with fruit at all stages of ripening from mature green to fully ripe. The hydroxycinnamyltransferase of chilled tomatoes falls rapidly on transfer to 20° with a lag of about 4–8 hr and within 48 hr returns to that of unchilled fruit. The effects of such warming treatments are reversible since when a chilling period is resumed following warming to 20°, the rise in hydroxycinnamyltransferase activity is also resumed. Of the 5 other enzymes of phenylpropanoid metabolism studied, only PAL shows a similar increase in activity during low temperature storage although the activity of the other enzymes was maintained at higher levels in fruit at 2° than at 20°. The possible relationship between the behaviour of hydroxycinnamyltransferase activity at various temperatures and the known susceptibility of tomatoes to chilling injury is discussed.     

Effect of Heat Treatment on the Development of Polygalacturonase Activity in Tomato Fruit during Ripening

When mature green tomato fruits are stored at 22?C for 30 days,they ripen normally and soften, but if they are kept at 33?Cfor 15 days (heat treatment), then stored at 22?C they do notsoften. The effect of heat treatment on the development of polygalacturonase(PG, EC 3.2.1.15 [EC] ) activities in tomato fruits during storagetherefore was studied. When mature green tomato fruits werestored at 22?C, PG activity, which had not been detectable inthe fruits, appeared as the color changed and increased dramaticallythereafter. PG activity, however, did not appear during heattreatment. When heat-treated fruits were transferred to 22?C,PG activity appeared after a 6-day lag period and increasedduring the next 30 days at 22?C to about 15% of the value detectedin ripe tomato fruits. The PG in ripe tomato fruits was composed of two isoenzymesthat had different mol wts. A high molecular form (PG-1, molwt 100K) appeared during the early stage of ripening and a lowmolecular form (PG-2, mol wt 44K) a little later. PG-2 increasedvigorously during ripening and eventually accounted for mostof the enzyme activity in the ripe fruits. Only a single isoenzyme(Y-PG, mol wt 100K), however, was detected in heat-treated tomatofruits stored at 22?C for 30 days. PG-1 and Y-PG gave the samemol wt on Sephacryl S-200 gel nitration, but could be separatedby Toyopearl HW-55 F gel filtration. (Received October 31, 1983; Accepted February 20, 1984)     

The influence of temperature on weight loss from stored onion bulbs due to desiccation, respiration and sprouting

When onion bulbs were stored for 9 months at 2, 7.5, 15 or 25 °C and 70% r.h., the losses due to desiccation increased with temperature but less than 20 % was due to respiration at any of the storage temperatures. Respiration rates of onion bulbs transferred from 2 to 25 °C were higher from February onwards than those of bulbs stored continuously at 25 °C. Conversely, bulbs transferred from 25 to 2 °C respired less from February onwards than those kept at 2 °C. Sprouting, at the final assessment in June, was highest at 15 and 7.5 °C and lowest at 2 °C. Total weight loss was above 45 % in all the storage treatments except at 2 °C (12%). Storage at 7.5 °C is suitable until March but long-term storage until June requires low temperatures.     

Low night temperatures have a differential effect on the diurnal cycling of gene expression in cold–sensitive and tolerant tomatoes*

Abstract. Comparisons were made between the changes in mRNA levels induced by low night temperatures in the cold–sensitive tomato and two altitudinal ecotypes of the wild species L. hirsutum. Changes in mRNA levels were detected by resolving in vitro translation products of poly(A)⁺ RNA by 2-D PAGE. The treatment was applied by first growing plants in a thermoperiod of 25/18°C and then switching to 25/6°C. All tomatoes displayed a diurnal cycling in which a set of mRNAs accumulated at the end of the 18°C nights, whereas another accumulated at the end of the 25°C days. The accumulation of night specific mRNAs was inhibited by 6°C nights in the cold sensitive tomatoes while that of the tolerant one was only marginally affected. All tomatoes showed a similar reduction in the apparent turnover rate of the day specific mRNAs during the 6°C nights. Finally, low night temperatures induced the accumulation of six to eight mRNAs in all genotypes. This number increased by 15 in L. esculentum after the seventh night and are likely involved in stress response rather than acclimation/tolerance. The tomato is proposed as a genetic model to discriminate genes involved in acclimation/tolerance from those involved in stress response.     

Partial Purification and Characterization of Thermostable Acid Phosphatase from Thermoacidophilic Archaeon Sulfolobus acidocaldarius

Thermostable acid phosphatase (APase) from thermoacidophilic archaeon Sulfolobus acidocaldarius was isolated, partially purified, and characterized. The optimum pH and temperature of the enzyme for p-nitrophenylphosphate (pNPP) as a substrate were 5.0 and 70°C, respectively. The apparent K _m value was 1.9 mM. This APase showed a native molecular mass of 20 kDa on a gel filtration chromatography. Of the APase activity, 60% remained after 60 min of heat treatment at 75°C. To confirm whether the APase is active in the monomeric form, we attempted to elute the enzyme from SDS-polyacrylamide gels with Disk electrophoresis apparatus and renature the enzyme. The APase activity was recovered up to 50% in the 14- to 35-kDa range, and maximum around 25 kDa. These results suggest that this APase is monomeric protein. Received: 8 July 1999 / Accepted: 9 August 1999     

Resistance of cold-hardened winter rye leaves (Secale cereale L.) to photo-oxidative stress

Catalase and photosystem II (PSII) were strongly inactivated during exposure to 4 °C and moderate light in 22 °C-grown non-hardened leaves (NHL) of winter rye (Secale cereale L.), but highly resistant to photo-inactivation at low temperature in 4 °C-grown cold-hardened leaves (CHL). Resistance of CHL to chilling-induced photo-inactivation of catalase and PSII depended partially on more efficient de novo synthesis at 4 °C and partially on improved protection. Lower rates of chloroplast-mediated inactivation of catalase in vitro indicated that less reactive oxygen was released by chloroplasts from CHL than by chloroplasts from NHL. The contents of xanthophyll cycle carotenoids, α-tocopherol, ascorbate, glutathione, the activities of superoxide dismutase and glutathione reductase, and the tolerance against paraquat-induced photo-oxidative damage were greatly increased in CHL, relative to NHL. Zeaxanthin-related thermal energy dissipation was only of minor importance for paraquat-tolerance and protection of catalase in CHL. When CHL were transferred to a higher temperature of 22 °C the increased resistance to photo-inactivation of catalase and PSII and the increased paraquat-tolerance were largely lost within 3 d, whereas most non-enzymic and enzymic antioxidants retained higher levels than in NHL. The decline of resistance to photodamage during dehardening was not related to concomitant changes of antioxidants or antioxidative enzymes.     

Fate of Salmonella montevideo on and in raw tomatoes as affected by temperature and treatment with chlorine.

A study was undertaken to determine the survival patterns of Salmonella montevideo G4639 on and in tomatoes during storage and the efficacy of chlorine treatment on inactivation of the pathogen. The population of S. montevideo on the surfaces of inoculated tomatoes stored at 10 degrees C did not change significantly (P < 0.05) throughout an 18-day storage period. Significant increases in population occurred within 7 days and within 1 day when tomatoes were stored at 20 and 30 degrees C, respectively. A significantly higher number of cells was taken up by the core tissue of tomatoes tempered at 25 degrees C when the tomatoes were dipped in a suspension at 10 degrees C compared with the number taken up when the tomatoes were dipped in cell suspensions tempered at 25 or 37 degrees C. Populations remained constant throughout subsequent storage for 8 days at 10 degrees C, regardless of the temperature differential between tomatoes and the dip suspension. Storage of tomatoes at 20 degrees C, however, resulted in significant increases in populations of S. montevideo. Populations of the pathogen on the surfaces and in the core tissues of tomatoes were significantly reduced by dipping for 2 min in a solution containing 60 or 110 ppm (60 or 110 micrograms/ml) chlorine, respectively; however, treatment in solution containing 320 ppm chlorine did not result in complete inactivation. Populations of S. montevideo remained unchanged in chopped tomatoes stored at 5 degrees C for 216 h (9 days) but increased significantly after storage for 96 or 22 h at 20 or 30 degrees C, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Low temperature alters plasma membrane lipid composition and ATPase activity of pineapple fruit during blackheart development

Plasma membrane (PM) plays central role in triggering primary responses to chilling injury and sustaining cellular homeostasis. Characterising response of membrane lipids to low temperature can provide important information for identifying early causal factors contributing to chilling injury. To this end, PM lipid composition and ATPase activity were assessed in pineapple fruit (Ananas comosus) in relation to the effect of low temperature on the development of blackheart, a form of chilling injury. Chilling temperature at 10 °C induced blackheart development in concurrence with increase in electrolyte leakage. PM ATPase activity was decreased after 1 week at low temperature, followed by a further decrease after 2 weeks. The enzyme activity was not changed during 25 °C storage. Loss of total PM phospholipids was found during postharvest senescence, but more reduction was shown from storage at 10 °C. Phosphatidylcholine and phosphatidylethanolamine were the predominant PM phospholipid species. Low temperature increased the level of phosphatidic acid but decreased the level of phosphatidylinositol. Both phospholipid species were not changed during storage at 25 °C. Postharvest storage at both temperatures decreased the levels of C18:3 and C16:1, and increased level of C18:1. Low temperature decreased the level of C18:2 and increased the level of C14:0. Exogenous application of phosphatidic acid was found to inhibit the PM ATPase activity of pineapple fruit in vitro. Modification of membrane lipid composition and its effect on the functional property of plasma membrane at low temperature were discussed in correlation with their roles in blackheart development of pineapple fruit.     

The effects of ethylene concentration in controlled atmosphere storage of tomatoes

Previous studies have demonstrated that mature green tomatoes can be stored for up to 10 wk at 12. 5°C, 93–95% r.h. in a controlled atmosphere (CA) containing 5% CO ₂ , 5% O₂ and 90% N ₂ , and will then ripen satisfactorily in air at 20°C. The effects of different concentrations of ethylene between <0.1 and 30 μl/litre in this storage atmosphere on ripening changes and fruit quality after 5 wk CA storage and a further 8 or 9 days ripening in air were investigated using cv. Sonatine glasshouse tomatoes. Maintaining ethylene concentrations in the storage atmosphere to.1 plllitre resulted in poor and uneven ripening of the tomatoes after storage, and increased their susceptibility to infection by Botrytis cinerea and Penicillium spp. Fruit previously stored in atmospheres containing 5 to 30 μl/litre ethylene were significantly softer after ripening than tomatoes stored in lower ethylene concentrations. Overall, the best results in terms of fruit quality (colour, firmness) and a low incidence of fungal infection were achieved with 1–3 μl/litre ethylene. The practical problems in achieving and maintaining optimum conditions, including the correct ethylene level, in CA storage of tomatoes are also discussed.     

Diclofenac Mediated Demodulation of Alkaline Phosphatase and Renal Cortical Damage in Experimental Albino Mice

Diclofenac sodium is known to interfere with renal physiology by inhibiting prostaglandins. Previous studies indicate that various nephrotoxins damage proximal renal tubules by altering alkaline phosphatase (APase) activity. APase has been reported to be a function related marker in renal proximal tubular epithelia where it is highly expressed. Present investigation deals with toxicity caused in mice kidney at histological and biochemical levels after diclofenac administration. Diclofenac toxicity was assessed by localizing APase in kidney histochemically and biochemically. Intramuscular diclofenac administration (10 mg/kg/body wt) for 30 days exhibited substantial degeneration in kidney. A marked change in APase activity was observed in histochemical and biochemical studies. A change was noticed in specific activity of APase at different periods of diclofenac treatment. Decrease in specific activity of APase after 10 days (18.41 %) and 30 days (55.3 %) of diclofenac exposure was observed. However, an insignificant hike in APase was observed after 20 days of drug therapy. Similar trends in APase activity were evidenced by the electrophoretic analysis. Histological and ultrastructural observations also corroborated above mentioned findings. Present investigation gives an insight into probable mechanism of renal pathology caused by diclofenac administration in mice.     

Glutamine synthetase in cultured whole retinas from the embryonic chick: Enhancement of basal and induced activity by 4 °C storage

Storage of whole retinas from the embryonic chick for 24 h at 4 °C resulted in increased basal levels of glutamine synthetase (GS) during subsequent incubation at 37 °C in the absence of cortisol. GS levels in these retinas maintained initially at 4 °C (CS), in many cases, exceeded GS levels in cortisol-induced whole retinas incubated solely at 37 °C. The increase in basal GS activity is seen within 48 h of the transfer of the retinas from 4 to 37 °C. If cortisol (0.001 μg/ml = 2.8 nm or 0.01 μg/ml = 28 nm) is added during the last 24 h of culture to CS retinas subsequently transferred to 37 °C, levels of GS are attained that are higher than those in the corresponding retinas cultured continually at 37 °C. However, the activity ratios (GS specific activity in cortisol-treated retinas/GS specific activity in retinas not exposed to cortisol) are similar for CS retinas and those maintained at 37 °C throughout. Monolayers of retinal cells display similar basal and cortisol-induced levels of GS independent of treatment. Retinal monolayers maintained at 4 °C for 24 h and subsequently incubated at 37 °C do not exhibit increases in either basal or cortisol-induced levels of GS over those in monolayers maintained at 37 °C throughout. The CS-promoted increase in the basal and cortisol-induced GS activity of whole retinas is eliminated by enzymatic dispersion of the retina just prior to 37 °C culture of the cells as monolayers. Both basal and cortisol-induced GS levels in the latter monolayers resemble those in retinal cells kept as monolayers throughout.     

Gene cloning, overproduction, and characterization of thermolabile alkaline phosphatase from a psychrotrophic bacterium

The gene encoding alkaline phosphatase from the psychrotrophic bacterium Shewanella sp. SIB1 was cloned, sequenced, and overexpressed in Escherichia coli. The recombinant protein was purified and its enzymatic properties were compared with those of E. coli alkaline phosphatase (APase), which shows an amino acid sequence identity of 37%. The optimum temperature of SIB1 APase was 50 degrees C, lower than that of E. coli APase by 30 degrees C. The specific activity of SIB1 APase at 50 degrees C was 3.1 fold higher than that of E. coli APase at 80 degrees C. SIB1 APase lost activity with a half-life of 3.9 min at 70 degrees C, whereas E. coli APase lost activity with a half-life of >6 h even at 80 degrees C. Thus SIB1 APase is well adapted to low temperatures. Comparison of the amino acid sequences of SIB1 and E. coli APases suggests that decreases in electrostatic interactions and number of disulfide bonds are responsible for the cold-adaptation of SIB1 APase.     

Glutamine synthetase in cultured whole retinas from the embryonic chick

Glutamine synthetase (GS) activity is enhanced in cultured whole retinas when a 72 h incubation at 37°C is preceded by storage at 4°C for 2–24 h. This enhancement occurs even in the absence of glucocorticoids and is maximal in retinas from 11 to 14 d embryos. In comparison, cortisol-induced increases in retinal GS activity at 37°C are optimal in retinas from 8 to 12 d embryos. This study, using cycloheximide (an inhibitor of protein synthesis) and cordycepin (an inhibitor of RNA synthesis), indicates that both protein and RNA synthesis are required for the 4°C storage enhancement of GS activity. The necessary RNA synthesis occurs within the first 48 h following transfer to 37°C and does not require concomitant protein synthesis. Uridine uptake, but not incorporation into trichloroacetic acid-precipitable material, is increased by initial 4°C storage when compared with whole retina controls incubated at 37°C for the total time. In contrast, both uptake and incorporation of amino acids are increased in 4°C-stored retinas for as long as 72 h subsequent to transfer from 4 to 37°C. This suggests that enhancement of GS activity may arise from a combination of elevated general protein synthesis and specific messenger-RNA synthesis following 4°C storage.     

Role of Aminocyclopropane-1-carboxylic Acid (ACC) in Control of Ethylene Production in Fresh and Cold-stored Rose Flowers

The relationships between ethylene production, aminocyclopropane-1-carboxylicacid (ACC) content and ethylene-forming-enzyme (EFE) activityduring ageing and cold storage of rose flower petals (Rose hybridaL. cv. Gabriella) were investigated. During flower ageing at20 °C there was a climacteric rise in petal ethylene production,a parallel increase in ACC content, but a continuous decreasein EFE activity. Applied ACC increased petal ethylene productionc. 200-fold. During cold storage of flowers at 1 °C therewere parallel increases in petal ethylene production and ACCcontent, to levels greater than those reached in fresh flowersheld at 20 °C. EFE activity decreased during storage. Immediatelyafter cold-stored flowers were transferred to 20 °C ethyleneproduction and ACC levels were c. four times greater than infreshly cut flowers. These levels increased to maximum valuesof two to four times the maximum values reached during ageingof fresh, unstored, flowers. It was concluded that in rose petalsethylene synthesis is probably regulated by ACC levels and thatcold storage stimulates ethylene synthesis because it increasesthe levels of ACC in the petals. Key words: Rose flower, senescence, ethylene     

High temperature inactivation of cucumber and alfalfa mosaic viruses in Nicotiana rustica cultures

Cucumber mosaic (CMV) and alfalfa mosaic (AlfMV) viruses could not be detected in Nicotiana rustica tissues cultured at 32 °C for 16–18 days or at 40 °C for 5 days, but infectivity remained high in comparable tissue cultured at 22 °C. Incubation of infected cultures at 28–30 °C resulted in an initial reduction followed by a partial recovery in the infectivity of both viruses. The infectivity of CMV in tissues grown between 12 and 32 °C was highest in cultures grown at 12 °C. Although CMV infectivity was not detected in cultures after 16–18 days at 32 °C, virus was eliminated only after a further 30 days at 32 °C. When cultures were transferred from 32 to 22 °C after shorter treatment periods, infectivity rapidly increased to levels higher than those of infected tissues grown continuously at 22 °C. At 40 °C, CMV was eliminated from infected tissues after 9 days and AlfMV after 7 days. Cultures grown continuously at 40 °C deteriorated rapidly but, when grown under diurnal alternating periods of 8 h at 40 °C and 16 h at 22 °C, they remained viable and CMV was also inactivated.     

The white-rot fungus Cerrena unicolor strain 137 produces two laccase isoforms with different physico-chemical and catalytic properties

Cerrena unicolor secreted two laccase isoforms with different characteristics during the growth in liquid media. In a synthetic low-nutrient nitrogen glucose medium (Kirk medium), high amounts of laccase (4,000 U l⁻¹) were produced in response to Cu²⁺. Highest laccase levels (19,000 U l⁻¹) were obtained in a complex tomato juice medium. The isoforms (Lacc I, Lacc II) were purified to homogeneity with an overall yield of 22%. Purification involved ultrafiltration and Mono Q separation. Lacc I and II had M _w of 64 and 57 kDa and pI of 3.6 and 3.7, respectively. Both isoforms had an absorption maximum at 608 nm but different pH optima and thermal stability. Optimum pH ranged from 2.5 to 5.5 depending on the substrate. The pH optima of Lacc II were always higher than those of Lacc I. Both laccases were stable at pH 7 and 10 but rapidly lost activity at pH 3. Their temperature optimum was around 60°C, and at 5°C they still reached 30% of the maximum activity. Lacc II was the more thermostable isoform that did not lose any activity during 6 months storage at 4°C. Kinetic constants (K _m, k _cat) were determined for 2,2′-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS), 2,6-dimethoxyphenol and syringaldazine.