Transglycosylations catalysed by Y151M mutant of human salivary α-amylase (HSA)

Biochemical and enzymatic characterisation has been achieved for the Tyr151Met (Y151M) mutant of human salivary α-amylase (HSA). Substantial transglycosylation capacity was detected in Y151M in addition to its hydrolytic activity. Y151M was capable of transferring maltose and maltotriose residues from a maltotetraose donor onto different 4-nitrophenyl glycosides resulting in the formation of 1-thio-β-D-glucosides, β- and α-D-glucosides and β-D-xylosides with DP 2-4 in yields up to 50%. Reactions were monitored using TLC, HPLC and MALDI-TOF MS. ¹H and ¹³C NMR studies revealed that the Y151M preserved its stereo- and regio-selectivity. Glycosylation took place at position 4 of the glycosyl acceptors, resulting in the new α-1,4-glycosidic bonds exclusively.