Model Study on Asymmetry-Inducing and Recognizing Ability of Peptide Chains

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The function of an enzyme consisting of proteins is explained by 'lock and key' theory, which is convenient to explain specificities of the enzyme, but it cannot explain fast enzymatic reaction. The applicant assumed that the conformation of peptide chains around the active site of an enzyme provides the specificity of enzyme, even if the space around active site is wide or is not controlled by peptide chains, and has gotten a few evidences that this assumption is correct on basis of model reactions. In first year, porphyrin complexes having peptide chains on the meso positions were synthesized as model of cytochrome P-450. These are completely different from models proposed so far, at the point that it has a wide space around active site, but nevertheless attained high asymmetric induction and high reaction rates at the same time, especially depending on the content of α-helix.. In second year, the applicant found that several glycoproteins are models of α-chymotrypsin and also found that they recognize R,S-configuration of amino acids by a-helix of the peptide conformation. In this year, a kind of glycoproteins were found to be esterase models in non-aqueous medium, but they do not seem to induce asymmetry of esterification products on basis of the β-sheet conformation.As mentioned above, it is proposed that the specificity of an enzyme is derived from α-helix of peptide chains, even if the space around the active site is not narrow as taught by 'key and lock' theory.