Beta-L-arabinofuranosidase, GH127. One member of this family, from Bidobacterium longicum, UniProtKB:E8MGH8, has been characterized as an unusual beta-L-arabinofuranosidase enzyme, EC:3.2.1.185. It rleases l-arabinose from the l-arabinofuranose (Araf)-beta1,2-Araf disaccharide and also transglycosylates 1-alkanols with retention of the anomeric configuration. Terminal beta-l-arabinofuranosyl residues have been found in arabinogalactan proteins from a mumber of different plantt species. beta-l-Arabinofuranosyl linkages with 1-4 arabinofuranosides are also found in the sugar chains of extensin and solanaceous lectins, hydroxyproline (Hyp)2-rich glycoproteins that are widely observed in plant cell wall fractions. The critical residue for catalytic activity is Glu-338, in a ET/SCAS sequence context.
Cyclases involved in the biosynthesis of lantibiotics, and similar proteins. LanC is the cyclase enzyme of the lanthionine synthetase. Lanthionine is a lantibiotic, a unique class of peptide antibiotics. They are ribosomally synthesized as a precursor peptide and then post-translationally modified to contain thioether cross-links called lanthionines (Lans) or methyllanthionines (MeLans), in addition to 2,3-didehydroalanine (Dha) and (Z)-2,3-didehydrobutyrine (Dhb). These unusual amino acids are introduced by the dehydration of serine and threonine residues, followed by thioether formation via addition of cysteine thiols, catalysed by LanB and LanC or LanM. LanC, the cyclase component, is a zinc metalloprotein, whose bound metal has been proposed to activate the thiol substrate for nucleophilic addition. A related domain is also present in LanM and other pro- and eukaryotic proteins with poorly characterized functions.
Cyclases involved in the biosynthesis of class II lantibiotics, and similar proteins. LanM-like proteins. LanM is a bifunctional enzyme, involved in the synthesis of class II lantibiotics. It is responsible for both the dehydration and the cyclization of the precursor-peptide during lantibiotic synthesis. The C-terminal domain shows similarity to LanC, the cyclase component of the lan operon, but the N terminus seems to be unrelated to the dehydratase, LanB.