What is it about?
Some bacterial GH5_5 endoglucanases are endowed with transglycosylation activity while the fungal counterparts are not. Structural adaptations must exist to explain such a difference. We've characterized Ps_Cel5A, a GH5_5 of Pseudomonas stutzeri, and demonstrated its hydrolytic and transglycosylating activities. In addition, we've determined its structure, enabling the comparison with the structures of fungal GH5_5 enzymes. While the negative subsites are well conserved, the positive subsites displayed two major adaptations. Firstly, two positively charged residues, an arginine and a lysine, are present in the positive subsites of Ps_Cel5A. Secondly, a disulfide bridge is absent in Ps_Cel5A, increasing flexibility of the positive subsites.
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Why is it important?
Our results show the adaptation of the positive subsites of Ps_Cel5A linked to transglycosylation. They corroborate also our previous study on RBcel1, another bacterial GH5_5 endoglucanase/transglycosylase. Both enzymes have an arginine residue in the +1/+2 subsites. This arginine residue is, however, not conserved indicating a convergent evolution.
Perspectives
Despite its lack of originality, I hope that people will enjoy reading our article. Many researchers are more interested in carbohydrate degradation and less on synthesis. Somehow, our article may provoke reflection and interest as the topic is a bit off the beaten track.
PhD Raphael Dutoit
LABIRIS
Read the Original
This page is a summary of: Crystal structure determination ofPseudomonas stutzeriA1501 endoglucanase Cel5A: the search for a molecular basis for glycosynthesis in GH5_5 enzymes, Acta Crystallographica Section D Structural Biology, June 2019, International Union of Crystallography,
DOI: 10.1107/s2059798319007113.
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