Abstract：
:β-N-Acetylhexosaminidases (CAZy GH20, EC 3.2.1.52) are exo-glycosidases specific for cleaving N-acetylglucosamine and N-acetylgalactosamine moieties of various substrates. The β-N-acetylhexosaminidase from the filamentous fungus Talaromyces flavus (TfHex), a model enzyme in this study, has a broad substrate flexibility and outstanding synthetic ability. We have designed and characterized seven glycosynthase-type variants of TfHex mutated at the catalytic aspartate residue that stabilizes the oxazoline reaction intermediate. Most of the obtained enzyme variants lost the majority of their original hydrolytic activity towards the standard substrate p-nitrophenyl 2-acetamido-2-deoxy-β-D-glucopyranoside (pNP-β-GlcNAc); moreover, the mutants were not active with the proposed glycosynthase donor 2-acetamido-2-deoxy-d-glucopyranosyl-α-fluoride (GlcNAc-α-F) either as would be expected in a glycosynthase. Importantly, the mutant enzymes instead retained a strong transglycosylation activity towards the standard substrate pNP-β-GlcNAc. In summary, five out of seven prepared TfHex variants bearing mutation at the catalytic Asp370 residue acted as efficient transglycosidases, which makes them excellent tools for the synthesis of chitooligosaccharides, with the advantage of processing an inexpensive, stable and commercially available pNP-β-GlcNAc.
journal_name
Int J Biol Macromoljournal_title
International journal of biological macromoleculesauthors
Kapešová J,Petrásková L,Kulik N,Straková Z,Bojarová P,Markošová K,Rebroš M,Křen V,Slámová Kdoi
10.1016/j.ijbiomac.2020.05.273subject
Has Abstractpub_date
2020-10-15 00:00:00pages
1206-1215eissn
0141-8130issn
1879-0003pii
S0141-8130(20)33474-7journal_volume
161pub_type
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