Hydrophobic fluorescent group coupled to Taka‐amylase A. Change of its environment accompanying splitting of disulfide bonds

Native Taka‐amylase A (α‐amylase produced by Asp. oryzae) was coupled with 1‐dimethylaminonaphthalene‐5‐sulfonyl chloride. When disulfide bonds of the modified enxyme were split by reduction or by reduction and subsequent carboxymethylation, its fluorescent properties changed markedly. It was suggested that the hydrophobic dye group is incorporated into a hydrophobic region as the consequence of the flexibility gained by the polypeptide chain by the cleavage of disulfide bonds.