Abstract: In accordance with the subject invention, novel DNA sequences, heterologous constructs and plant expression vectors are provided which relate to the metallocarboxypeptidase inhibitor (MCPI) protein. MCPI protein is capable of inactivating metallocarboxypeptidase, exopeptidase-type digestive enzymes. In addition, this application relates to plant cells and plant entities, including whole plants, plant seed, and plant parts, containing such constructs and methods of providing transgenic plants capable of inhibiting metallocarboxypeptidase (MCP) proteinases and methods of using such for the tolerence of MCPI sensitive pests.