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Effect of condensed tannins prepared from several forages on the in vitro precipitation of ribulose‐1,5‐ bis phosphate carboxylase (Rubisco) protein and its digestion by trypsin (EC 2.4.21.4) and chymotrypsin (EC 2.4.21.1)
Author(s) -
McNabb Warren C,
Peters Jason S,
Foo L Yeap,
Waghorn Garry C,
Jackson Felicity S
Publication year - 1998
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(199806)77:2<201::aid-jsfa26>3.0.co;2-j
Subject(s) - rubisco , sephadex , biochemistry , trypsin , proanthocyanidin , hydrolysis , ribulose 1,5 bisphosphate , chemistry , lotus corniculatus , tannin , chymotrypsin , biology , botany , food science , enzyme , polyphenol , antioxidant
A series of in vitro experiments was undertaken to determine the extent to which Sephadex LH‐20 treated extracts from a range of temperate forages precipitated ribulose‐1,5‐ bis phosphate carboxylase (Rubisco) and affected the enzymatic hydrolysis of Rubisco protein by trypsin and chymotrypsin at a range of pH values. Rubisco was chosen because it represents the principal dietary protein for ruminants fed fresh forages. Condensed tannins (CT) or proanthocyanidins (PA) are routinely purified by chromatography using Sephadex LH‐20 as a matrix. However, these extracts contained non‐CT phenolics together with PA so the term ‘CT extract’ was preferred to ‘PA’ to describe the extracts. The in vitro precipitation of Rubisco provided a means to compare the reactivity of the CT extracts. The amount of CT extract required to precipitate all the Rubisco in 10 μg of total soluble leaf protein from white clover ( Trifolium repens ) when this protein was incubated with CT extracts of Lotus corniculatus , L pedunculatus and sainfoin ( Onobrychis viciifolia ) was similar, with between 25 and 50 μg of extract required. The CT extract of sulla ( Hedysarum coronarium ) also precipitated all the Rubisco, however this only occurred with 50 μg of the extract. The CT extract of dock ( Rumex obtusifolius ) precipitated all the Rubisco when 5 μg of extract or greater was incubated with total soluble leaf protein. However, the differences between the reactivity of all these CT extracts at a range of pH values appeared to be small. Condensed tannin extracts of L corniculatus and L pedunculatus partially inhibited the hydrolysis of Rubisco by trypsin and chymotrypsin to a similar extent, but the extent of the inhibition was affected by pH. The inhibition was greater at pH 6·0 than 7·0, whilst at pH 8·0, CT extracts had little or no affect on trypsin and chymotrypsin. It was concluded that, although the precipitation of Rubisco provided an ideal method for comparing CT extracts, reactivity alone was unlikely to account for the differences in nutritive value that occur with forages containing CT. © 1998 SCI.