Biological and synthetic receptors for three different types of pest species have been compared: valinomycin and calix[4]crown ethers for K+, urease and metallomacrocycles for urea, and phosphate binding proteins and synthetic anion receptors for different anions. The symbiosis of synthetic and biological receptors is demonstrated for transesterification reactions of amino acid esters by alpha-chymotrypsin in organic solvents in the presence of crown ethers.