Identification of Thermotoga maritima MSB8 GH57 α-amylase AmyC as a glycogen-branching enzyme with high hydrolytic activity

Xuewen Zhang, Reinder Leemhuis, Stefan Janecek, Maria Martinovicova, Tjaard Pijning, Marc van der Maarel*

*Bijbehorende auteur voor dit werk

OnderzoeksoutputAcademicpeer review

2 Citaten (Scopus)
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AmyC, a glycoside hydrolase family 57 (GH57) enzyme of Thermotoga maritima MSB8, has previously been identified as an intracellular α-amylase playing a role in either maltodextrin utilization or storage polysaccharide metabolism. However, the α-amylase specificity of AmyC is questionable as extensive phylogenetic analysis of GH57 and tertiary structural comparison suggest that AmyC could actually be a glycogen-branching enzyme (GBE), a key enzyme in the biosynthesis of glycogen. This communication presents phylogenetic and biochemical evidence that AmyC is a GBE with a relatively high hydrolytic (α-amylase) activity (up to 30% of the total activity), creating a branched α-glucan with 8.5% α-1,6-glycosidic bonds. The high hydrolytic activity is explained by the fact that AmyC has a considerably shorter catalytic loop (residues 213-220) not reaching the acceptor side. Secondly, in AmyC, the tryptophan residue (W 246) near the active site has its side chain buried in the protein interior, while the side chain is at the surface in Tk1436 and Tt1467 GBEs. The putative GBEs from three other Thermotogaceae, with very high sequence similarities to AmyC, were found to have the same structural elements as AmyC, suggesting that GH57 GBEs with relatively high hydrolytic activity may be widespread in nature.

Originele taal-2English
Pagina's (van-tot)6141–6151
Aantal pagina's11
TijdschriftApplied Microbiology and Biotechnology
Nummer van het tijdschrift15
Vroegere onlinedatum13-jun-2019
StatusPublished - aug-2019

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