Complete sequence, subunit structure, and complexes with pancreatic alpha-amylase of an alpha-amylase inhibitor from Phaseolus vulgaris white kidney beans.
The complete amino acid sequence of a white kidney bean (Phaseolus vulgaris) alpha-amylase inhibitor (PHA-I), which is composed of two kinds of glycopolypeptide subunits, alpha and beta, was established by conventional methods. The polypeptide molecular weight of PHA-I determined by the light-scattering technique, considered together with the sequence molecular weights revealed for the subunits, indicated that PHA-I has the subunit stoichiometry of (alpha beta)2 complex. Inhibition test of PHA-I with increasing amounts of porcine pancreatic alpha-amylase (PPA) suggested that an inactive 2:1 complex is formed between PPA and PHA-I. In fact, two complexes differing from each other in the molar ratio of PPA to PHA-I were separated by gel filtration, and molecular weight estimation by the light-scattering technique confirmed that they are complexes of PHA-I with one or two PPA molecules. The binding of PPA to PHA-I appeared to follow simple binomial statistics, suggesting that two binding sites on PHA-I are independent and of high affinity for PPA.
Kasahara
K
K
Department of Applied Biological Chemistry, College of Agriculture, Osaka Prefecture University.
Hayashi
K
K
Arakawa
T
T
Philo
J S
JS
Wen
J
J
Hara
S
S
Yamaguchi
H
H
D000595:Amino Acid Sequence; D000818:Animals; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D007887:Fabaceae / Q000737:chemistry*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010179:Pancreas / Q000201:enzymology*; D010446:Peptide Fragments / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D010946:Plants, Medicinal; D011487:Protein Conformation; D013552:Swine; D014361:Trypsin Inhibitors; D000516:alpha-Amylases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism
D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D010940:Plant Proteins; D014361:Trypsin Inhibitors; D000516:alpha-Amylases