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Novel functions can emerge in an enzyme family while conserving catalytic mechanism, motif or fold. PLP-dependent enzymes have evolved into seven fold types and catalyse diverse reactions using the same mechanism for the formation of external aldimine. Nucleotide sugar aminotransferases (NSATs) and dehydratases (NSDs) belong to fold type I and medi...
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Context 1
... factors governing product identity -clues from 3D structures: We superposed the 3D structures of three C3 NSATs and three C4 NSATs bound to substrates in the form of external aldimine ( Table 2). The backbone conformation is highly similar in these six proteins ( Figure 3A). ...Context 2
... conformation of ligands is identical in C3 NSATs ( Figure S5B); in the other three, i.e., C4 NSATs, the pyranose ring either flips or shifts ( Figure S5C, S5D). A tyrosine residue H-bonds with the Nacetyl / -OH group at C2 in all three crystal structures and this residue is conserved in C3_hits (Table 2) PseC (PDB id 2FNU), but these were not considered for analysis -the ligand conformation was deemed uncertain based on a visual inspection of the fit of the structure to the electron density ( ...Context 3
... on the pyranose ring carbon which is aminated, NSATs are further classified as C3 NSATs and C4 NSATs. These, in turn, can install amine either axially or equatorially (assuming 4 C1 conformation) (Table S2 and S3). ...Context 4
... conformation of the pyranose ring has been so chosen that the substituent at C5 (i.e., the highest numbered chiral carbon in the pyranose ring) is oriented equatorially. Schematic structures of reactants and products are given in Tables S2 and S3 . CC-BY-ND 4.0 International license perpetuity. ...