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O-GlcNAcylation is an essential protein glycosylation governed by two O-GlcNAc cycling enzymes: O-GlcNAc transferase (OGT) installs a single sugar moiety N- acetylglucosamine (GlcNAc) on protein serine and threonine residues, and O-GlcNAcase (OGA) removes them. Aberrant O-GlcNAcylation has been implicated in various diseases. However, the large repertoire of more than 1000 O-GlcNAcylated proteins and the elusive mechanisms of OGT/OGA in substrate recognition present significant challenges in targeting the dysregulated O-GlcNAcylation for therapeutic development. Recently, emerging evidence suggested that the non-catalytic domains play critical roles in regulating the functional specificity of OGT/OGA via modulating their protein interactions and substrate recognition. Here, we discuss recent studies on the structures, mechanisms, and related tools of the OGT/OGA non-catalytic domains, highlighting new opportunities for function-specific control. [ABSTRACT FROM AUTHOR]

• O-GlcNAc modification of nuclear and cytoplasmic proteins is critical in metazoan biology. • The enzymes OGT and OGA attach and remove O-GlcNAc, respectively. • OGT also cleaves an essential cell cycle regulator using the same active site as it does for protein glycosylation. • Structures of OGT and OGA help explain catalytic mechanisms and promiscuous substrate recognition, and show how inhibitors bind. • OGA substrates bind in two different backbone orientations, but adopt a similar V-shaped binding conformation. Dysregulation of nuclear and cytoplasmic O-linked β- N -acetylglucosamine (O-GlcNAc) cycling is implicated in a range of diseases including diabetes and cancer. This modification maintains cellular homeostasis by regulating several biological processes, such as cell signaling. This highly regulated cycle is governed by two sole essential enzymes, O-GlcNAc transferase and O-GlcNAcase that add O-GlcNAc and remove it from over a thousand substrates, respectively. Until recently, due to lack of structural information, the mechanism of substrate recognition has eluted researchers. Here, we review recent successes in structural characterization of these enzymes and how this information has illuminated key features essential for catalysis and substrate recognition. Additionally, we highlight recent studies which have used this information to expand our understanding of substrate specificity by each enzyme. [ABSTRACT FROM AUTHOR]

Abstract: Tin nano-particles are employed in the Barbier-type allylation reaction of carbonyl compounds in water to afford the corresponding homoallylic alcohols in good yields. The in situ generated allylation intermediates, allyltin(II) bromide and diallyltin dibromide, have been directly observed by using 1H NMR. A mechanism is proposed based on this observation. [Copyright &y& Elsevier]

Zn/CdSO4 and Zn/SnCl2 bimetal systems were employed in the allylations of aldehydes or ketones in distilled water to afford the corresponding homoallylic alcohols in good yields. Also, the chemoselectivity was studied under the same condition. It was found that good chemoselectivity of allylations could be obtained for different carbonyl compounds under the mediation of our bimetal systems. [Copyright &y& Elsevier]