The number of amino acids in a genetic code

Abstract

It is generally accepted that the universal genetic code evolved from a simpler form that employed fewer amino acids. We have recently developed a ‘simplified genetic code’ only using 19 amino acids. Simplified codes will provide not only new insights into primordial genetic codes, but also an essential protein engineering tool for the assessment of the early stages of protein evolution and for the improvement of pharmaceuticals. In this review, we describe the evolution of the number of amino acids in a genetic code. We also discuss the utility of engineered genetic codes having a different number of amino acids from that of the universal code.