Subsite mapping of porcine pancreatio alpha-amylase I and II using 4-nitrophenyl-α-maltooligosaccharides

Article abstract of DOI:10.1016/0008-6215(94)00335-D

The catalytic efficiency (k_cat/K_m) and the cleaved bond distribution for the nitrophenylated maltooligosaccharides, p-NPGIc_n (2<*>n<*>7) hydrolysed by porcine pancreatic alpha-amylase isozymes I and II were determined. the subsite affinities (A_i) were calculated from the p-NPGlc_n (4<*>n<*>7) hydrolysis data.Five subsites (-3 to 2) bind glucosidic residues with a positive affinity.No additional subsites could be detected both at the reducing end (3,4,5)and at the nonreducing end (-4,-5,-6).The energetic profiles of both isozymes are similar.The energetic profile of PPA differs from other alpha-amylases by having both a small number of subsites, and a catalytic subsite with a high positive affinity.Excellent agreement was found between observed catalytic efficiency values and those calculated from the subsite affinities. Keywords: alpha-Amylase isozymes; Active centre; Subsite structure; Energetic profile; Porcine pencreatic alpha-amylaseKeywords: alpha-Amylase isozymes; Active centre; Subsite structure; Energetic profile; Porcine Pancreatic alpha-amylase