Acid Protease from Germinated Sorghum

Abstract

The substrate specificity of the sorghum acid protease was elucidated using synthetic peptides and pancreatic ribonuclease A as substrates. These studies revealed that the enzyme has a rather narrow and novel specificity requirement. The protease specifically cleaves the peptide linkages involving the α‐carboxyl group of either aspartic acid or glutamic acid with the release of the acyl portion of these acidic amino acids. Further, the side chain carboxyl groups of aspartic acid and glutamic acid in the peptides should be unsubstituted for the enzyme to act on the peptide, and therefore, glutaminyl and asparaginyl peptides are not cleaved by the enzyme. Studies carried out with performate oxidized ribonuclease and ribonuclease methyl esters have further substantiated the results obtained with the synthetic substrates. These results suggest that the sorghum acid protease will be very valuable in sequence analyses of proteins.