Fig. 5. Proteolytic inhibition in alfalfa extracts requires relatively little PPO or o-diphenol. (A) Alfalfa extracts (2 mg mL^–1 protein) of varying PPO concentration were prepared by mixing PPO- and Control-Alfalfa extracts to give the desired level of PPO activity. The resulting extracts were incubated with (•) or without () 3 mM caffeic acid as indicated and proteolysis, as amino acid release after 4 h, was measured. PPO activity (caffeic acid substrate) is given as nkat mL^–1. (B) Control- () or PPO- containing (•, 4.17 nkat mL^–1) alfalfa extracts (2 mg mL^–1 protein) were incubated with various levels of caffeic acid and proteolysis, as amino acid release after 4 h, was measured. Results for both experiments are the average 6 SEM of three experiments using independently prepared extracts.