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Separation and characterisation of chymotryptic peptides from α‐ and β‐purothionins of wheat
Author(s) -
Mak Alan S.,
Jones Berne L.
Publication year - 1976
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740270302
Subject(s) - chymotrypsin , hydrolysis , chemistry , residue (chemistry) , tyrosine , leucine , phenylalanine , acid hydrolysis , amino acid , peptide , chromatography , biochemistry , enzyme , trypsin
Both α‐ and β‐purothionins of wheat were readily hydrolysed by chymotrypsin into peptides which were separable by ion exchange chromatography. Hydrolysis occurred rapidly at the single tyrosine residue but there was no apparent cleavage at the phenylalanine residue. Leucine residues were hydrolysed at a slower rate. Reduction and alkylation of the purothionins increased the rate at which they were hydrolysed by chymotrypsin. Seventeen peptides were isolated from α‐purothionin digests and β‐purothionin yielded 15. From amino acid analyses of the chymotryptic peptides, there were at least four differences in the primary structures of the purothionins with β‐purothionin containing 2 Asx, 1 Lys and 0.5 Leu residues which had replaced 2 Gly, 1 Arg and 0.5 Ileu residues of α‐purothionin. Tyrosine is probably the thirteenth residue from the amino terminus of both α‐ and β‐purothionins.