title: In vitro study of red clover polyphenol oxidase activity, activation, and effect on measured lipase activity and lipolysis.
abstract: The goal of this paper was, first, to study the effect of red clover polyphenol oxidase (PPO) activity on protein-bound phenols and measured lipase activity in vitro and, second, to study the effect of PPO activation, measured as an increase in protein-bound phenols, as a result of degrees of damaging (not damaged, crushed, and freeze/thawed) of red clover before wilting on measured enzyme activity and in vitro lipid metabolism when incubated in a phosphate buffer. There was a positive relation between PPO activity and the occurrence of protein-bound phenols with a concomitant decrease in measured lipase activity, indicating a possibility to a direct inhibition of enzymes as a result of protein-bound phenols. Furthermore, damaging can activate PPO in red clover, measured as an increase in protein-bound phenols during wilting [0.7-20.6 nmol of tyrosine equiv (mg of protein)(-1)], again with a concomitant decrease in measured lipase activity [41.3-20.3 mumol of p-nitrophenyl butyrate (PNPB) min(-1) (mg of protein)(-1)]. Lipid metabolism during incubation of these forages in a phosphate buffer with ascorbic acid was only influenced by damaging when wilted for 24 h, with a lower lipolysis in crushed and freeze/thawed (52.9 and 32.6%, respectively, after 8 h of incubation) material compared to all other treatments (on average 60.4% after 8 h of incubation).
authors: Institute for Agriculture and Fisheries Research, Unit Plant, Applied Genetics and Breeding, Caritasstraat 21, 9090 Melle, Belgium.
authors: G
authors: G
authors: Van Ranst
authors: V
authors: V
authors: Fievez
authors: M
authors: M
authors: Vandewalle
authors: J
authors: J
authors: De Riek
authors: E
authors: E
authors: Van Bockstaele
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D008049:Lipase / Q000032:analysis* / Q000378:metabolism; D050356:Lipid Metabolism; D008066:Lipolysis; D010636:Phenols / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D029921:Trifolium / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism
chemical_list: D010636:Phenols; D010940:Plant Proteins; D004156:Catechol Oxidase; D008049:Lipase