Functional Derivatives of Lignin Sulfonic Acid

Ritter, D. M.; Olleman, E. D.; Pennington, Derrol; Wright, K. A.

doi:10.1021/ja01159a073

Cited by 8 publications

(1 citation statement)

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“…In the present study, we compared the transient-state kinetic constants of P. eryngii VP (and its W164S variant) and P. chrysosporium LiP on native (20–30 % phenolic) and nonphenolic (derivatized) softwood and hardwood lignosulfonates. With this purpose, samples were methylated with methyl iodide [ 44 ], which has advantages with respect to other methylating agents applied to lignosulfonates [ 45 , 46 ].…”

Section: Discussionmentioning

confidence: 99%

Role of surface tryptophan for peroxidase oxidation of nonphenolic lignin

Sáez-Jiménez

Rencoret

Rodrı́guez-Carvajal

et al. 2016

Biotechnol Biofuels

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BackgroundDespite claims as key enzymes in enzymatic delignification, very scarce information on the reaction rates between the ligninolytic versatile peroxidase (VP) and lignin peroxidase (LiP) and the lignin polymer is available, due to methodological difficulties related to lignin heterogeneity and low solubility.ResultsTwo water-soluble sulfonated lignins (from Picea abies and Eucalyptus grandis) were chemically characterized and used to estimate single electron-transfer rates to the H2O2-activated Pleurotus eryngii VP (native enzyme and mutated variant) transient states (compounds I and II bearing two- and one-electron deficiencies, respectively). When the rate-limiting reduction of compound II was quantified by stopped-flow rapid spectrophotometry, from fourfold (softwood lignin) to over 100-fold (hardwood lignin) lower electron-transfer efficiencies (k 3app values) were observed for the W164S variant at surface Trp164, compared with the native VP. These lignosulfonates have ~20–30 % phenolic units, which could be responsible for the observed residual activity. Therefore, methylated (and acetylated) samples were used in new stopped-flow experiments, where negligible electron transfer to the W164S compound II was found. This revealed that the residual reduction of W164S compound II by native lignin was due to its phenolic moiety. Since both native lignins have a relatively similar phenolic moiety, the higher W164S activity on the softwood lignin could be due to easier access of its mono-methoxylated units for direct oxidation at the heme channel in the absence of the catalytic tryptophan. Moreover, the lower electron transfer rates from the derivatized lignosulfonates to native VP suggest that peroxidase attack starts at the phenolic lignin moiety. In agreement with the transient-state kinetic data, very low structural modification of lignin, as revealed by size-exclusion chromatography and two-dimensional nuclear magnetic resonance, was obtained during steady-state treatment (up to 24 h) of native lignosulfonates with the W164S variant compared with native VP and, more importantly, this activity disappeared when nonphenolic lignosulfonates were used.ConclusionsWe demonstrate for the first time that the surface tryptophan conserved in most LiPs and VPs (Trp164 of P. eryngii VPL) is strictly required for oxidation of the nonphenolic moiety, which represents the major and more recalcitrant part of the lignin polymer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0615-x) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Role of surface tryptophan for peroxidase oxidation of nonphenolic lignin

Sáez-Jiménez

Rencoret

Rodrı́guez-Carvajal

et al. 2016

Biotechnol Biofuels

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The comprehensive analysis of grasses

Waite

Gorrod

1959

J Sci Food Agric

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An attempt has been made to account quantitatively for the main groups of chemical compounds in the dry matter of grasses. This was done by successive extractions with ethanol‐benzene, warm water and ammonium oxalate solution, followed by digestion with pepsin and a delignifying treatment to isolate a holocellulose fraction. The polysaccharides in the holocellulose were determined. It was found possible to account for 97–98% of the grass dry matter and to identify all but 1–3% of it. The use to which such detailed knowledge can be put to provide a better assessment of the feeding value of grass is discussed.

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