Show simple item record Winters, Ana L. Minchin, Frank R. Michaelson-Yeates, Terry P. T. Lee, Michael R. F. Morris, Phillip 2009-05-26T09:22:25Z 2009-05-26T09:22:25Z 2008-03-25
dc.identifier.citation Winters , A L , Minchin , F R , Michaelson-Yeates , T P T , Lee , M R F & Morris , P 2008 , ' Latent and Active Polyphenol Oxidase (PPO) in Red Clover (Trifolium pratense) and Use of a Low PPO Mutant To Study the Role of PPO in Proteolysis Reduction ' Journal of Agricultural and Food Chemistry , vol 56 , no. 8 , pp. 2817-2824 . , 10.1021/jf0726177 en
dc.identifier.issn 1520-5118
dc.identifier.other PURE: 104534
dc.identifier.other dspace: 2160/2389
dc.description IMPF: 02.56 RONO: 1920 4063 en
dc.description.abstract Polyphenol oxidase (PPO) activity in leaf extracts of wild type (WT) red clover and a mutant line expressing greatly reduced levels of PPO (LP red clover) has been characterized. Both latent and active forms of PPO were present, with the latent being the predominant form. PPO enzyme and substrate (phaselic acid) levels fluctuated over a growing season and were not correlated. Protease activation of latent PPO was demonstrated; however, the rate was too low to have an immediate effect following extraction. A novel, more rapid PPO activation mechanism by the enzyme’s own substrate was identified. Rates of protein breakdown and amino acid release were significantly higher in LP red clover extracts compared with WT extracts, with 20 versus 6% breakdown of total protein and 1.9 versus 0.4 mg/g FW of free amino acids released over 24 h, respectively. Inclusion of ascorbic acid increased the extent of protein breakdown. Free phenol content decreased during a 24 h incubation of WT red clover extracts, whereas protein-bound phenol increased and high molecular weight protein species were formed. Inhibition of proteolysis occurred during wilting and ensilage of WT compared with LP forage (1.9 vs 5 and 17 vs 21 g/kg of DM free amino acids for 24 h wilted forage and 90 day silage, respectively). This study shows that whereas constitutive red clover PPO occurs predominantly in the latent form, this fraction can contribute to reducing protein breakdown in crude extracts and during ensilage. en
dc.format.extent 8 en
dc.language.iso eng
dc.relation.ispartof Journal of Agricultural and Food Chemistry en
dc.title Latent and Active Polyphenol Oxidase (PPO) in Red Clover (Trifolium pratense) and Use of a Low PPO Mutant To Study the Role of PPO in Proteolysis Reduction en
dc.type Text en
dc.type.publicationtype Article (Journal) en
dc.contributor.institution Institute of Biological, Environmental and Rural Sciences en
dc.description.status Peer reviewed en

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