Abstract
The effect of a chloroform/methanol extract of a peptic digest of several proteins on Ca2+/calmodulinstimulated rat brain phosphodiesterase I (PDE I) was investigated. The concentration of the extract from zein producing 50% inhibition of the PDE I was 144μg/ml. This value was 4 to 8 times lower than that for extracts of other proteins, such as ovalbumin, soy protein, and casein. The extract from zein had little or no effect on the activity of PDE I in the absence of calmodulin. These observations suggest that the extract from zein may contain some potent calmodulin-antagonistic peptide. Using an ODS column (Cosmosil C18), chloroform/methanol-extracted peptides from the peptic digest of zein were separated into several fractions. The most effective fraction produced 50% inhibition of Ca2+/calmodulinstimulated PDE I at 53μg/ml, and this fraction was purified to homogeneity. The sequence of the peptide was found to be AGILPLSPLF, which is identical to part of B-zein.
