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SUBUNIT STRUCTURES AND ESSENTIAL AMINO ACID RESIDUES OF WHITE KIDNEY BEAN ( PHASEOLUS VULGARIS ) α‐AMYLASE INHIBITORS
Author(s) -
HO M. FRANK,
WHITAKER JOHN R.
Publication year - 1993
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.1993.tb00859.x
Subject(s) - chemistry , amino acid , alanine , peptide , phaseolus , biochemistry , glycine , peptide sequence , stereochemistry , serine , enzyme , biology , botany , gene
Both white kidney bean α‐amylase inhibitors WKB 858A (MW 42,000) and WKB 858B (MW 20,000) were composed of two subunits as determined by N‐terminal amino acid analysis by amino acid sequence, by SDS‐PAGE and by separation on a chromatofocusing column in 8 M urea. N‐Terminal amino acids for Inhibitor WKB 858A were alanine and glycine, with a sequence of H 2 N‐Ala‐Glu‐Asn‐Ala‐Gly‐Thr‐Tyr–COOH for deglycosylated 9,000 MW peptide and H 2 N‐Gly‐Asn–COOH for deglycosylated 12,000 MW peptide. N‐Terminal amino acids for Inhibitor WKB 858B were alanine and serine, with a sequence of H 2 N‐Ala‐Thr‐Glu‐Thr‐Ser–COOH for the deglycosylated 9,000 MW peptide and H 2 N‐Ser‐Ala‐Val‐Gly‐Leu‐Asp‐Phe‐Val‐Leu‐Val‐Pro‐Val‐Gin‐Pro‐Glu‐Ser‐Lys‐Gly‐Asp‐Thr‐VaVal‐Glu‐Phe‐Asp–COOH for the deglycosylated 15,000 MW peptide. Chemical modification of 2 of 7 His residues with diethylpyrocarbonate resulted in 26% loss of inhibitory activity. Modification of 1.5 of 7 Trp residues with N‐bromosuccinimide gave 60% loss of inhibitory activity. Modification of 2 of 6 Tyr residues with N‐acetylimidazole gave 60% loss of inhibitory activity. Modification of 3.6 of 6 Arg residues with p‐hydroxyphenylglyoxal gave 64% loss of inhibitor activity. These results indicate the possible importance of one or more His, Trp, Tyr and perhaps Arg residues for inhibitory activity against porcine pancreatic α‐amylase.