Dehydrogenation enzymes

Nakatsubo, F. Higuchi, T. Enzymic dehydrogenation ofp-coumaryl alcohol. III. Analysis of dilignols by gas chromatography and NMR spectrometry. Wood Res. 1975, 58, 12-19. 

It has been proposed that dehydrodiferulic acid units are formed by enzymic dehydrogenation of two ferulic acid units ester-linked to the cell wall (15). As can be seen from Table I, only very small amounts of the acid were found in cell walls it seems unlikely that such amounts are sufficient to have a large effect on limiting the biodegradation of the walls. 

Lignin, a phenolic polymer, is also incorporated into the wall during the secondary-thickening phase. This component permeates the spaces between the plant cells, thereby strengthening the tissue. Lignification is a result of enzymic dehydrogenation and subsequent polymerization of coumaryl, coniferyl, and sinapyl alcohols, the relative proportions of which differ in the lignins from different plants.23-28... 

Fig. 4-4. Formation of resonance-stabilized phenoxy radical by the enzymic dehydrogenation of coniferyl alcohol (Adler, 1977).

The enzymic dehydrogenation reaction is initiated by an electron transfer which results in the formation of resonance-stabilized phenoxy radicals (Fig. 4-4). The combination of these radicals produces a variety of dimers and oligomers, termed lignols (Fig. 4-5). 

JC Pew and WJ Connors. New Structures from the Enzymic Dehydrogenation of Lignin Model/)-Hydroxy-a-carbinols. J. Org. Chem. 34 580-584, 1969. 

Nakatsubo, F. (1981) Enzymic dehydrogenation of p-coumaryl alcohol and syntheses of oligolignols. Wood Research 67, 59-118. 

K Ogiyama, T Kondo. On the pinoresinol type of structural units in lignin molecule. IV. The changes of dUactone-yield during enzymic dehydrogenation. Mokuzai Gakkaishi 14 416 20, 1968. 

JC Pew, WJ Connors. New structures from the enzymic dehydrogenation of lignin model p-hydroxy-a-carbinols. 7 Org Ctem 34 580-584, 1969. 

Obtained by enzymic dehydrogenation of propioguaiacone with horseradish peroxidase in water in the presence of hydrogen peroxide at 30° for 1 h (60%) (compound 10) [7161]. 

The pregnenolone resultant from cholesterol cleavage is transformed in main to progesterone by a simple enzymic dehydrogenation of the 3j8 hydroxyl function to the 3-keto group. This reaction is DPN specific (Halkerston et ah, 1961). The shift of the J bond to the J position accompanies the oxidation. The mechanism of reaction of the isomerase involved here (Talalay, 1957) is interesting. There is apparently an internal transfer of hydrogen from C-4 to C-6 (Fig. 11). No incorporation... 

---