Veratryl alcohol, effects

To study the effect of veratryl alcohol, purified lignin peroxidase or unfractionated enzyme preparation was incubated with buffer, pH 3.0 or 5.0. The concentration of veratryl alcohol in the incubation mixture was 0, 10 or 100 mM. Incubation times were 38 days at 20°C and 40 days at 4°C. The protein concentration of purified enzyme was 80/tg/ml and of unfractionated preparation 180 tg/ml. The incubation mixtures were sterile filtered to prevent microbial growth. 

Effect of Veratiyl Alcohol. At pH 5.0 the purified lignin peroxidase was not inactivated under the conditions tested. At pH 3.0 the enzyme lost its activity when incubated at 20°C for 38 days, and the presence of veratryl alcohol could not stabilize it. 100 mM veratryl alcohol even inactivated the enzyme to some extent. Ionic strength did not significantly affect the activities. The effect of veratryl alcohol was the same when unfractionated enzyme was used. This time the ionic strength in the activity assay mixture affected the activities, probably because one enzyme in the unfractionated preparation is sensitive to high ionic strength 12),... 

Aitken and Irvine 17) have recently reported on the stability characteristics of lignin peroxidases. They also have shown that the enzyme was most stable at pH 4.5, although higher pH values were not tested. The stability was dependent on protein concentration and veratryl alcohol had a stabilizing effect. The latter result was contrary to our experience. 

Figure 4. Biodegradation of HCl/dioxane-isolated C-labeled straw lignin by 50 mL washed P. chrysosporium mycelial pellets ( ) in the presence of 2.5 units glucose oxidase accelerative effect engendered by 2 units lignin peroxidase in absence (Q) and presence (H) of 75 /imole veratryl alcohol. Adapted and redrawn from reference 34.

The combined effect of laccase and VAO on ABTS was determined as follows. The reagent (0.03%) was oxidised with purified laccase from P. sajor-caju (0.004 U/mL). After the appearance of the green (ABTS+ ) colour, VAO (0.07 U/mL) and veratryl alcohol (1 mM) was added and the decrease in colour was observed visually. 

MY Balakshin, CL Chen, JS Gratzl, AG Kirkman, H Jakob. Kinetic studies on oxidation of veratryl alcohol by laccase-mediator system. Part 1. Effects of mediator concentration. Holzforschung 54(2) 165-170, 2000. 

Interestingly, ABTS was much less effective as a redox mediator than HA when P. cinnabarinus laccase acted on III. Moreover, veratryl alcohol (which is a non-substrate for laccase alone) was efficiently converted to veratraldehyde by laccase when ABTS was added to the reaction mixture, whereas less than 10% was oxidised to the aldehyde when the mediator was HA. The reason of this mechanistic difference in regioselectivity of... 

In addition to catalyzing the oxidation of many compounds, LiP is also able to catalyze reductive reactions in the presence of electron donors such as EDTAor oxalate (Fig. 7) (6, 77). Veratryl alcohol is a free radical mediator in these reactions. The electron donors appear to be oxidized by a LiP generated veratryl alcohol cation radical. The resulting anion radical can catalyze the reduction of good electron acceptors such as cytochrome c, nitroblue tetrazolium, and oxygen. Evolution of CO2 from EDTA or oxalate effectively drives the reductive reactions. Similar reactions have also been observed with the manganese dependent peroxidases in the presence of quinones (20). Early work performed in our laboratory showed that these reductive mechanisms are not involved in TNT reduction. However, these reactions may be involved in other steps in TNT metabolism. 

Figure 9. Effect of increasing amounts of hydroxylaminodinitrotoluenes on the veratryl alcohol oxidase activity of lignin peroxidase H8 (32). The reaction mixture contained in a final volume of 600 pi 0.05 pM lignin peroxidase H8, 40 mM sodium tartrate buffer, pH 3.5, 130 pM H2O2, 5.6 mM veratryl alcohol, and various concentrations of hydroxylaminodinitrotoluene (both isomers) [pM] 0, 5,A 10, 16, O 21, A 24, .

The effect of the initial concentration of veratryl alcohol on the duration of the lag period during oxidation of hydroxylaminodinitrotoluene was investigated (Fig. 11). The length of the lag period was directly related to the veratryl alcohol concentration, up to 2.8 mM, thus indicating its role as a radical cation mediator in the oxidation of hydroxylaminodinitrotoluene. Surprisingly, the activity of the lignin peroxidase that reappeared was also affected by the concentration of veratryl alcohol. The rates were lower when veratryl alcohol was below 1.1 mM (Fig. 11). A value of 167 pM was determined for veratryl alcohol and lignin peroxidase H2 at pH 3.5 (50). 

An unexpected result was the effect of H202on the lag phase and the lignin peroxidase activity at constant levels of veratryl alcohol and inhibitor (Fig. 12). An increase of the concentration of H2O2 from 64 pM to 512 pM in the assay mixture led to an extension of the lag period. At lower H202-concentrations, down to 13 pM, the veratryl alcohol oxidase... 

The conversion of tetrahydroberberine into tetrahydropalmatine, first achieved by Spath and Lang, is described elsewhere (p. 292). By demethylenating berberine sulphate Sp th and Quietensky obtained the dihydric phenolic base (XXV R = R = H), which on complete 0-methylation yielded palmatine (XXV R = R = Me), and on partial methylation gave jatrorrhizine (XXV R = H R = Me), the latter being isolated and identified as di-tetrahydrojatrorrhizine (p. 291). Columbamine is represented by (XXV R = Me R = H). A complete synthesis of palmatine was effected by Haworth, Koepfli and Perkin, who condensed 3 4-dimethoxyAomophthalic anhydride with 8-veratryl-ethylamine to -j8-veratrylethyl-3 4-dimethoxy omophthalamic acid, the methyl ester (XXVI) of which was converted by treatment with phosphorus oxychloride into oxypalinatine (XXVII), CjiHjiO N, buff-coloured prisms, m.p. 183°. This behaves like oxyberberine (XXII, p. 335), and on electrolytic reduction yields dZ-tetrahydropalmatine, m.p. 147°, which on oxidation with iodine in alcohol furnished palmatine (XXV R = R = Me) in the form of the iodide, m.p. 241° (dec.). 

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