New serine carboxypeptidase in mung bean seedling cotyledons.

Two serine carboxypeptidases (EC 3.4.16.5) were purified from mung bean seedling cotyledons. Sequences of tryptic peptides derived from the 42.5 kD enzyme corresponded to the derived amino acid sequence of a sequenced cDNA (GenBank U49382 and U49741). This enzyme exhibited the substrate specificity pattern previously published for mung bean carboxypeptidase I. In comparison, the sequence and substrate specificity data obtained for the 43 kD enzyme were similar but not identical. Both enzymes showed preference for peptide substrates with a large hydrophobic residue at the C-terminus. With regard to the penultimate residue of peptide substrates, the mung bean carboxypeptidase I preferred small aliphatic amino acid residues, while the 43 kD enzyme preferred large hydrophobic ones.