Subsite mapping of porcine pancreatic alpha-amylase I and II using 4-nitrophenyl-α-maltooligosaccharides
✍ Scribed by El Hassan Ajandouz; Guy J. Marchis-Mouren
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 540 KB
- Volume
- 268
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
The catalytic efficiency (kcat/K m) and the cleaved bond distribution for the nitrophenylated maltooligosaccharides, p-NPGlc 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-NPGIc 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.