N-terminal catalytic domain of 4-alpha-glucanotransferase; glycoside hydrolase family 57 (GH57)
4-alpha-glucanotransferase (TLGT, EC 2.4.1.25) plays a key role in the maltose metabolism. It catalyzes the disproportionation of amylose and the formation of large cyclic alpha-1,4-glucan (cycloamylose) from linear amylose. TLGT functions as a homodimer. Each monomer is composed of two domains, an N-terminal catalytic domain with a (beta/alpha)7 barrel fold and a C-terminal domain with a twisted beta-sandwich fold. Some family members have been designated as alpha-amylases, such as the heat-stable eubacterial amylase from Dictyoglomus thermophilum (DtAmyA) and the extremely thermostable archaeal amylase from Pyrococcus furiosus(PfAmyA). However, both of these proteins are 4-alpha-glucanotransferases. DtAmyA was shown to have transglycosylating activity and PfAmyA exhibits 4-alpha-glucanotransferase activity.
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