Submitted to: International Grasslands Congress
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2004
Publication Date: 6/26/2005
Citation: Marita, J.M., Hatfield, R.D., Brink, G.E. 2005. Polyphenol oxidase activity and in vitro proteolytic inhibition in grasses. In: O'Mara, F.P., Wilkins, L., 't Mannetje, D.K., Lovett, R.A., Rogers, M., Boland, T.J., editors. XX International Grassland Congress: Offered Papers. Paper# 220. Interpretive Summary:
Technical Abstract: Harvesting and storing high quality forage in the cool humid regions of agricultural production remains a challenge due to the potential high degree of protein degradation during ensiling. Red clover is an exception with high protein levels at harvest that are maintained during ensiling. Decreased proteolytic activity in red clover is due to polyphenol oxidase (PPO) activity and appropriate o-diphenol substrates. This project was undertaken to determine if PPO activity is present in a range of grasses and the potential role in proteolytic inhibition in the presence of the o-diphenol caffeic acid. The amount of PPO activity measured in each grass varied significantly depending upon the species and upon the specific type of o-diphenol used as the primary PPO substrate. Orchardgrass, meadow fescue, ryegrass, and smooth bromegrass exhibited the highest PPO activities. Chlorogenic acid and/or caffeic acid were the preferred substrates, although there were differences among the most active grasses as to which was the best utilized. This suggests potential differences among the individual PPO enzymes. Generally, the addition of caffeic acid to isolated grass extracts resulted in proteolytic inhibition in grasses with substantial PPO activity. Such results suggest that several important grass species contain PPO activity, but may lack the appropriate o-diphenol substrates to effectively inhibit proteolysis. Initial results suggest that proteolytic inhibition can be achieved with the addition of caffeic acid.