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Forages

Proteolysis and Characterization of Peptidases in Forage Plants

Facultad de Agronomía e Ingeniería Forestal, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Macul, Santiago, Chile

^* Corresponding author (gpichard{at}uc.cl)

Received for publication September 8, 2005. Plant peptidases are involved in protein degradation in the rumen of grazing animals, but little is known about the variation in their activity under anaerobic conditions at 39°C. We investigated the activity of endogenous peptidases in 342 accessions of grass and legume forages and the molecular weight and class of peptidases in a subsample of them. Proteolytic activity was measured by in vitro incubation of tissue over a gelatin substrate. Molecular weight and class of peptidases were assessed by zymograms. A wide range in proteolytic activity index (PAI) was detected (mean PAI = 0.35, ranged from 0.00 to 1.30). More than 88% of the observed variance was due to differences in genus, species, and cultivar. Most of the species had one main peptidase, and their molecular weights ranged from 54 to 130 kDa. In the six species tested, proteases present corresponded to the serine class. The wide variation in proteolysis observed and the predominant occurrence of one peptidase of the same enzyme class support the idea that a reduction of protease activity in forages can be achieved by genetic improvement.

Abbreviations: PAI, proteolytic activity index