The Effects of Chemical Modification by N-Bromosuccinimide of Saccharifying α-Amylase from Bacillus subtilison Various Substrates*

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Abstract
The effects of chemical modification by N-bromosuccinimide (abbreviated as NBS)** of saccharifying α-amylase from Bacillus subtilisupon the hydrolysis of several substrates, i.e., maltooligosaccharides (Gn; G2 to G15), phenyl α-maltoside (øM) and cyclo-heptaamylose (CG7), and also upon glucosyl transfer from maltose to phenyl α-gluco-side (øG), were studied. The effects of the chemical modifiication on the rates of enzyme reaction at three molar ratios of [NBS][Enzyme] were significantly dependent' on the substrates. The effect decreases in the order; hydrolysis of CG7≃hydrolysis of øM into G and øG≃ glucosyl transfer from G2 to øhydrolysis of øM into ø and G2≃hydrolysis of maltooligosaccharides, G2˜G15. The following trends are noteworthy: i)The effect on maltooligosaccharides is relatively small and almost independent of the degree of polymerization, ii) Distinct differences in the effects are observed for the two different modes of hydrolysis of øM ; the rate of øM→G+øG is much more strongly affected than that of øM→ø+G2. iii) The effect on CG7 is considerably larger than that on the maltooligosaccharides. iv) The effect on glucosyl transfer from G2 to øG is remarkable in comparison with that on the hydrolysis of maltooligosaccharides. Based on these results, the location and the role of the modified tryptophan residue were discussed.

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