Fig. 4.

Substrate competition experiment. (A) Diagram showing competing substrates (peptides 2 and S2). (B) Percent conversion of directed and undirected peptides in competition reactions at 1, 10, and 100 μM (2, 20, and 200 μM total peptide) by indicated enzyme. Raw data points are represented by black dots superimposed on plots. Data bars present mean values +/− SEM across three distinct reactions (n=3). Error bars are centered on the mean. (C) Model of alternative modes of interaction between the enzymes and substrate at varying concentrations of substrate. K_M^{Active site} is the affinity (K_M) of substrate binding directly to the active site.