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Publication Abstract from PubMed

Rhizobium etli, a nitrogen-fixing bacterial symbiont of legume plants, encodes an essential L-asparaginase (ReAV) with no sequence homology to known enzymes with this activity. High-resolution crystal structures of ReAV show indeed a structurally distinct, dimeric enzyme, with some resemblance to glutaminases and beta-lactamases. However, ReAV has no glutaminase or lactamase activity, and at pH 9 its allosteric asparaginase activity is relatively high, with Km for L-Asn at 4.2 mM and kcat of 438 s(-1). The active site of ReAV, deduced from structural comparisons and confirmed by mutagenesis experiments, contains a highly specific Zn(2+) binding site without a catalytic role. The extensive active site includes residues with unusual chemical properties. There are two Ser-Lys tandems, all connected through a network of H-bonds to the Zn center, and three tightly bound water molecules near Ser48, which clearly indicate the catalytic nucleophile.

Crystal structures of the elusive Rhizobium etli L-asparaginase reveal a peculiar active site.,Loch JI, Imiolczyk B, Sliwiak J, Wantuch A, Bejger M, Gilski M, Jaskolski M Nat Commun. 2021 Nov 18;12(1):6717. doi: 10.1038/s41467-021-27105-x. PMID:34795296^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.