3 hydroxyanthranilic acid 3haa

Crystalline l-tryptophan (Trp, ≥98%), l-kynurenine (Kyn, ≥98%), 3-hydroxy-ᴅ,l-kynurenine (3HKyn), kynurenic acid (Kyna, ≥98%), nicotinamide (NAm, ≥99.5%), xanthurenic acid (XA, 96%), quinolinic acid (QA, 99%), 3-hydroxyanthranilic acid (3HAA), anthranilic acid (AA), 3-nitro-l-tyrosine (3NT), ammonium acetate (eluent additive for LC-MS), acetic acid (LC-MS grade), formic acid (LC-MS grade), trichloroacetic acid (TCA), activated charcoal, and bovine serum albumin (BSA) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Methanol (MeOH, hypergrade), acetonitrile (ACN, hypergrade), hydrochloric acid (HCl), and ammonium hydroxide were acquired from Merck (Darmstadt, Germany). Stock solutions of Trp, Kyn, Kyna, XA, 3HAA, and AA were prepared by dissolving a reagent in dimethyl sulfoxide (DMSO, Merck, Darmstadt, Germany), 3HKyn in water acidified to pH 2.5 with HCl, NAm and QA in MeOH, and 3NT in 0.1% (v/v) formic acid in water. The stock solutions were stored at −20 °C and used for up to three freeze and thaw cycles. Working solutions at intermediate concentrations were prepared daily by dilution in methanol.

Ascorbic acid, hydroquinone, 3-hydroxyanthranilic acid (3HAA), resveratrol, catechin, caffeic acid, tannic acid, ferulic acid, sinapic acid, and ABTS (2, 2′-azinobis(3-ethylbenzthiazoline-6-sulfonate) were obtained from Sigma Aldrich (Saint Louis, USA). Stock solutions of 100 mM were made in either water (Ascorbic acid, hydroquinone, ABTS and tannic acid) or pure ethanol (3HAA, resveratrol, catechin, caffeic acid, ferulic acid and sinapic acid) and kept at -20 °C in the dark. Commercial cellulase mixtures Celluclast 1.5L and Novozym188 were obtained from Novozymes A/S, Denmark. The Celluclast 1.5L mixture had a protein content of 127 mg/g, containing 62 FPU/g cellulase activity and 15 U/g β-glucosidase activity. Novozym188 had a protein content of 220 mg/g, containing 231 U/g β-glucosidase activity. Purified Thielavia terrestris LPMO (TtLPMO9E, previously TtGH61E17 ), was obtained from Novozymes A/S. PcLPMO9D (previously known as PcGH61D) from Phanerochaete chrysosporium was cloned and expressed in Pichia pastoris and purified according to34 (link).