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GrainGenes Reference Report: PPS-122-425

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Reference	PPS-122-425
Title	Purification and characterization of barley dipeptidyl peptidase IV
Journal	Plant Physiology
Year	2000
Volume	122
Pages	425-431
Author	Davy A [ Show all 6 ]
Abstract	Summary: Barley (Hordeum vulgare L.) storage proteins, which have a high content of proline (Pro) and glutamine, are cleaved by cysteine endoproteases to yield peptides with a Pro next to the N-terminal and/or C-terminal amino acid residues. A peptidase cleaving after Xaa-Pro- at the N terminus of peptides was purified from green barley malt. It was identified as a serine-type dipeptidyl peptidase (DPP), based on inhibitor studies, and the nature of the cleavage product. It is a monomeric glycoprotein with an apparent molecular mass of 105 kD (85 kD after deglycosylation), with a pI of 3.55 and a pH optimum at 7.2. Substrate specificity was determined with a series of fluorogenic peptide substrates with the general formula Xaa-Pro-AMC, where Xaa is an unspecified amino acid and AMC is 7-amino-4-methylcoumarin. The best substrates were Xaa = lysine and arginine, while the poorest were Xaa = aspartic acid, phenylalanine, and glutamic acid. The K(m) values ranged from 0.071 to 8.9 micromolar compared with values of 9 to 130 micromolar reported for mammalian DPP IVs. We discuss the possible role of DPP IV in the degradation of small Pro-containing peptides transported from the endosperm to the embryo of the germinating barley grain
Keyword	[ Hide all but 1 of 39 ] amino acid amino acid sequence arginine barley barley-grain characterization cleavage cysteine degradation embryo endoproteases endosperm enzyme activity enzyme inhibitors germinating barley glutamine glycoprotein glycoproteins hordeum vulgare inhibitor isoelectric point lysine malt molecular weight n-terminus peptidases peptide ph proline protein degradation purification residue residues specificity storage storage protein substrate substrate-specificity yield

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