A cysteine endopeptidase from barley malt which degrades hordein

A cysteine endopeptidase of M r 29 000 which we have named malt endopeptidase-1 (MEP-1) was purified to homogeneity from a four-day green malt of barley ( Hordeum vulgare cv Schooner). It consists of two main species of pl 4.2 and 4.3 has a pH optimum of 4.5 for the hydrolysis of hordein and account...

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Bibliographic Details
Published in:Phytochemistry (Oxford) 1989, Vol.28 (12), p.3285-3290
Main Authors: Phillips, Hilary A., Wallace, William
Format: Article
Language:English
Subjects:
Analytical, structural and metabolic biochemistry
barley malt
Biological and medical sciences
chemical constituents of plants
chemical degradation
cysteine
cysteine endopeptidase
enzyme activity
Enzymes and enzyme inhibitors
food composition
Fundamental and applied biological sciences. Psychology
Gramineae
hordein
hordein degradation
Hordeum
Hordeum vulgare
Hydrolases
malt
proteinases
purification
seeds
substrate specificity
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Summary:A cysteine endopeptidase of M r 29 000 which we have named malt endopeptidase-1 (MEP-1) was purified to homogeneity from a four-day green malt of barley ( Hordeum vulgare cv Schooner). It consists of two main species of pl 4.2 and 4.3 has a pH optimum of 4.5 for the hydrolysis of hordein and accounts for over a half of the hordein degrading activity in the malt. It is inhibited by p-chloromercuriphenolsulphonic acid and leupeptin. MEP-1 also hydrolyses haemoglobin and azocasein and while the activity on the latter is stimulated two-fold by 5 mM 2-mercaptoethanol (2-ME) the hydrolysis of hordein is increased 11-fold at this concentration of the thiol. MEP-1 hydrolysed a range of N- t-butoxycarbonyl- l-amino acid- p-nitrophenyl esters; the highest activity was obtained with the derivatives of glutamine, alanine and leucine. A polyclonal antibody to MEP-1 cross reacted with a 37 000 M r endopeptidase present at low activity.
ISSN:0031-9422
1873-3700
DOI:10.1016/0031-9422(89)80332-2