The present invention relates to the cloning and expression of a nucleotide sequence encoding a premature α-amylase inhibitor (PMAI) protein and amino acid sequence having 100% sequence identity with the mature Amaranth α-amylase inhibitor (AAI) polypeptide sequence isolated from Amaranthus hypochondriacus. Further it includes recombinant constructs and anti-insecticidal compositions comprising strong amylase inhibitory (AI) activity against storage insect pest amylases. Additionally, present invention provides a signal peptide fused to the protein of interest that facilitates the extracellular secretion of the synthesized α-amylase inhibitor protein which results in significant inhibition of sucking pests of plants in agriculture.