“…The first crystal structure to be elucidated was of E. coli GGT (EcGGT) in 2006; in fact, three different structures of EcGGT (PDB IDs: 2DBU, 2D5G, 2DBX) were determined simultaneously (Table 2; Okada et al, 2006). Thereafter, GGT structures from a variety of microbes such as H. pylori (HpGGT), B. subtilis (BsGGT), B. licheniformis (BlGGT), B. anthracis (BanGGT; CapD), Bacillus halodurans (BhGGT), Pseudomonas nitoreducens (PnGGT), and Thermoplasma acidophilum (TaGGT) were determined (Boanca et al, 2007;Okada et al, 2007;Williams et al, 2009; Wu et al, 2009; Wada et al, 2010;Ida et al, 2014;Pica et al, 2016;Kumari et al, 2017; Table 2). Although the mammalian GGTs were the first to be described in detail, heavy glycosylation and membranebound localization made it difficult to determine their structure; the first crystal structure of human GGT was solved in 2013 (West et al, 2013).…”