title: Perennial peanut (Arachis glabrata Benth.) contains polyphenol oxidase (PPO) and PPO substrates that can reduce post-harvest proteolysis.
abstract: BACKGROUND
  Studies of perennial peanut (Arachis glabrata Benth.) suggest its hay and haylage have greater levels of rumen undegraded protein (RUP) than other legume forages such as alfalfa (Medicago sativa L.). Greater RUP can result in more efficient nitrogen utilization by ruminant animals with positive economic and environmental effects. We sought to determine whether, like red clover (Trifolium pretense L.), perennial peanut contains polyphenol oxidase (PPO) and PPO substrates that might be responsible for increased RUP.
  
  
  RESULTS
  Perennial peanut extracts contain immunologically detectible PPO protein and high levels of PPO activity (>100 nkatal mg(-1) protein). Addition of caffeic acid (PPO substrate) to perennial peanut extracts depleted of endogenous substrates reduced proteolysis by 90%. Addition of phenolics prepared from perennial peanut leaves to extracts of either transgenic PPO-expressing or control (non-expressing) alfalfa showed peanut phenolics could reduce proteolysis >70% in a PPO-dependent manner. Two abundant likely PPO substrates are present in perennial peanut leaves including caftaric acid.
  
  
  CONCLUSIONS
  Perennial peanut contains PPO and PPO substrates that together are capable of inhibiting post-harvest proteolysis, suggesting a possible mechanism for increased RUP in this forage. Research related to optimizing the PPO system in other forage crops will likely be applicable to perennial peanut.
authors: US Dairy Forage Research Center, Agricultural Research Service, US Department of Agriculture, Madison, WI 53706, USA. michael.sullivan@ars.usda.gov
authors: Michael L
authors: ML
authors: Sullivan
authors: Jamie L
authors: JL
authors: Foster
mesh_terms: D000818:Animals; D010367:Arachis / Q000201:enzymology*; D002109:Caffeic Acids / Q000378:metabolism; D004156:Catechol Oxidase / Q000378:metabolism*; D004032:Diet / Q000662:veterinary*; D000455:Medicago sativa / Q000201:enzymology / Q000378:metabolism*; D010636:Phenols / Q000378:metabolism; D010936:Plant Extracts / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified; D059748:Proteolysis; D012418:Ruminants
chemical_list: D002109:Caffeic Acids; D010636:Phenols; D010936:Plant Extracts; D010940:Plant Proteins; D004156:Catechol Oxidase; C040048:caffeic acid; C515101:caftaric acid