Regulation of cyclic nucleotide phosphodiesterase (PDE) by zein peptides

We have prepared zein peptides and characterized their ability to regulate the activity of cyclic nucleotide phosphodiesterase (PDE) isozymes obtained from canine heart ventricle. Native-zein inhibited 42%, 18% and 25% of the activities of PDE1, PDE2, and PDE4, respectively. AT1 was prepared by partial hydrolysis of the native-zein with 0.3 N HCl at 50 degrees C for 24 hr. The AT1 increased the activities of 63% and 40% of PDE1 and PDE4. AT1 was hydrolyzed with pepsin, chymotrypsin, thermolysin, and subtilisin. Pepsin- and chymotrypsin-treated AT1 increased the activity of PDE1 by 75%. Deaminated-zein were prepared by mild HCl hydrolysis (with 0.2 N HCl at 55 degrees C for 5 hr). Deamidation of zein had no effect on the activities of PDE1, PDE3, and PDE4. However, a deaminated-zein fraction (DA-3) increased PDE2 activity by 16%. From these results, it was confirmed that zein peptides had regulatory effects on PDE isozymes