May be involved in the degradation of small peptides (2-5 residues) or in the degradation of storage proteins in the embryo. Release of a C-terminal amino acid with broad specificity. Carboxypeptidase I is a dimer, where each monomer is composed of two chains linked by disulfide bonds. Secreted into the endosperm. After one day of germination, mainly found in the scutellum of the developing grain; barely detectable after four days, and absent from the mature grain. A lower level of expression is seen in the aleurone both during development and germination. The linker peptide is endoproteolytically excised during enzyme maturation. Belongs to the peptidase S10 family.