The core structure of class I MT is a Rossmann-like α/β fold, class II contain a TIM-barrel β/α core domain, class III has a tetrapyrrole methylase α/β fold structure, while class IV and class V include the SPOUT α/β structure and an all-β SET domain 18.īecause class I MTs show the highest diversity, they are subclassified according to the substrate specificity for small molecule, DNA, RNA, lipid and protein, plus several other uncharacterized enzymes 17. There are five known families of SAM-dependent MT (class I-V) with distinct protein folds of the catalytic domain 18. O-directed MTs are the most abundant (54%), whereas C-directed MTs constitute only 18%. Regarding transmethylation, about 120 members of SAM-dependent MTs have been classified (EC 2.1.1.X) based on their substrate specificity and on the targeted atom for methylation 17. Notably, sibiromycin effectively competes with the other two antibiotics and also has a faster reaction rate 14.Īs the second most widely used enzyme substrate (after ATP), SAM is not only a source of methyl group for transmethylation via S N2 mechanism 15, but it also provides homocysteine for transsulfuration and supplies aminopropyl group for aminopropylation 16. All these compounds are capable of forming covalent DNA-antibiotic adducts and are potent antitumor drugs. For example, having a C9-hydroxyl group in sibiromycin and anthramycin can cause cardiotoxicity 1, 3, 9, 10 O-glycosylation of sibirosamine at C7 significantly enhances the DNA binding affinity of sibiromycin 3, 5, 11, 12, 13. Different tricyclic ring substitutions of PBDs result in distinct biological activities. S1), where tomaymycin has a hydroxyl group. Sibiromycin and anthramycin are both derived from 3-H4MK with a common C8-methyl group ( Supplementary Fig. It depends on the specific moieties of individual antibiotic. The precise sequence of reactions that turn out the PBD antibiotics has been characterized biochemically. Sibiromycin, anthramycin and tomaymycin are PBD derivatives with a pharmacophore consisting of a tricyclic moiety (anthranilate, diazepine, and hydropyrrole) that is biosynthesized by combining l-tryptophan, l-tyrosine, and l-methionine 2, 8. Our results provide information to design L–L separation units with the capacity to selectively recover targeted molecules from pyrolysis oils.A schematic representation of the Ss-SibL enzymatic reaction. When using butanol as the solvent, the highest separation factor of total phenols over total sugars was observed. The partition coefficient of compounds of interest (both light and heavy fractions) is reported for the liquid–liquid equilibrium zone. Ternary phase diagrams for the organic solvent/water/bio-oil are reported. In this study, the use of liquid–liquid extraction with different solvents (1-butanol, ethyl acetate, 1-octanol, dichloromethane, toluene, and hexane) for the separation of targeted molecules (lignin oligomers, sugars, acetic acid) is explored. However, the obtained aqueous phase from this method still contains phenols and is diluted and difficult to use. Cold water precipitation of pyrolytic lignin from bio-oil is the most common approach used. Separating bio-oil by fractionation with different chemical compositions is a critical step to refine these oils and obtain high-value products.
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