Figure 5.

Substrate protects maize β-UP from inactivation by iodoacetamide. Samples of partially purified maize β-UP were treated with 1 mm iodoacetamide (IA) in the presence or absence of 10 mm β-ureidopropionate (S) for 30 min. After quenching the iodoacetamide by adding DTT to 10 mm, the samples were extensively dialyzed against 0.1 m potassium phosphate buffer containing 2 mm DTT and were then assayed for β-UP activity. The control sample was treated identically but had no iodoacetamide or substrate added.