Leucine Aminopeptidase in Eggs of the Soybean Cyst Nematode Heterodera glycines

Abstract

Supernatant from a sonicated macerate of eggs of Heterodera glycines hydrolyzed L-leucine beta-naphthylamide and L-leucine 7-amido-4-methylcoumarin. Rate of substrate hydrolysis was influenced by pH and increased with the duration of incubation. A Michaelis-Menten constant of 0.15 mM was obtained. Rate of substrate hydrolysis was decreased by freezing egg supernatant for 26 days or heating above 60 C for 5 minutes. When egg supernatant was incubated with six different substrates, L-leucine beta-naphthylamide was hydrolyzed most readily and L-valine beta-naphthylamide the least readily. The rate of substrate hydrolysis by egg supernatant was not increased by pretreatment of eggs with 3 mM zinc chloride for up to 14 days.