Protein-tannin complexes are susceptible to proteolytic
degradation.
A. Diaz-Hernandez, M.J. Nixon, F.M. Ball, R.A. Leng and J.B. Rowe
Department of Animal Science, UNE Armidale.
Proceedings of the New Zealand Society of Animal Production. 1997,
57: 116-119
In vitro studies were carried out to determine the
factors that affect formation and dissociation of the protein-tannin
complex (PTC) under conditions sumulating those found in the digestive
tract of the ruminant. For this study purified condensed tannins (CT)
from the following tropical plants were used: Acacia harpophylla,
Acacia aneura, Acacia saligna, Acacia holosericea, Tipuana tipu, Albizia
chinensis, Flemingia macrophylla, Grevilea robusta, Casuarina cristata,
Casuarina cunninghamiana, Azadarachta, Leucaena leucocephala, Leucaena
pallida and Leucaena diversifolia. English spinach was selected as
the source of soluble protein and during the growing phase, the plants
were exposed to a 14C-CO2 atmosphere for 48 h.
Following exposure, the foliar protein ribulose 1,5 biphosphate
carboxylase/oxygenase, (rubisco) was isolated. The radioactive labelled
protein was incubated with the isolated samples of CT for 2h at
39°C. The mixtures were then centrifuged and the percentages of
bound protein (precipitate) and unbound protein (fluid phase) were
determined. Formation of the protein-tannin complex (PTC) occurred over
a range of pH 3-7. Above this pH 7, no PTC was formed. To determine the
effects of pH on the dissociation of the PTC, the precipitate was
incubated with buffers over a range of pH 3-9. It was found that acidic
or alkaline pH was responsible for only 8 and 14% of the dissociation of
the PTC, respectively. However, addition of abomasal and intestinal
fluid from both sheep or cattle increased dissociation of PTC to more
than 60%. Further analysis showed that pepsin and trypsin are largely
responsible for the dissociation which occurs with the abomasal and
intestinal fluids respectively.
Keywords: NZSAPAB;
Condensed tannins; protein-tannin complex; tropical plants;
pepsin; trypsin.
Last Updated 12-09-1998
