Specificity of a wheat gluten aspartic proteinase.
The substrate and peptide bond specificities of a purified wheat gluten aspartic proteinase (GlAP) are studied. GlAP shows maximum gluten hydrolysing activity at pH 3.0. At this pH, especially the wheat high molecular weight glutenin subunits (HMW-GS) and to a lesser extent the low molecular weight glutenin subunits and gliadins are hydrolysed. GlAP has no obvious effect on albumins and globulins. In its action on oxidised insulin B-chain, GlAP forms eight peptides and has high specificity for peptide bonds located between amino acid residues with large hydrophobic side chains (Leu, Phe, Tyr) but the peptide bond Glu13-Ala14 is also hydrolysed. Although structurally quite similar to a barley aspartic proteinase, the peptide bond specificity of GlAP towards oxidised insulin B-chain resembles slightly more that of a cardoon aspartic proteinase, cardosin B. HMW-GS 7, purified from cultivar Galahad-77, is rapidly hydrolysed by GlAP. N-Terminal amino acid sequence data show that GlAP cleaves at least one Met-Ile peptide bond at the end of the N-terminal domain and two Val-Leu peptide bonds in the repetitive domain of HMW-GS 7.
Bleukx
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W
Katholieke Universiteit Leuven, Laboratorium voor Levensmiddelenchemie, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium.
Brijs
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K
Torrekens
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Van Leuven
F
F
Delcour
J A
JA
D000418:Albumins / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D005916:Globulins / Q000378:metabolism; D005983:Glutens / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007328:Insulin / Q000378:metabolism; D010455:Peptides / Q000032:analysis; D010940:Plant Proteins / Q000378:metabolism; D017421:Sequence Analysis; D013379:Substrate Specificity; D014908:Triticum / Q000201:enzymology*
D000418:Albumins; D005916:Globulins; D007328:Insulin; D010455:Peptides; D010940:Plant Proteins; D005983:Glutens; D016282:Aspartic Acid Endopeptidases