The Creation of a New Gene from a Redundant Duplicate of an Old Gene

Abstract

The type of gene duplication which produced the group of isozyme genes contributed greatly to the evolution of increasingly complex organisms. These functionally diverged duplicated genes, however, still specify the same enzyme in that their products act upon the same substrate with the help of the same coenzyme. A, B and C-subunits of LDH of any vertebrate must still maintain either the identical active site sequence of 12 amino acids (— Val-Ile-Ser-Gly-Gly-Cys-Asn-Leu-Asp-Thr-Ala-Arg —), or a sequence very similar to the above, for this is the sequence which binds with NAD and recognizes pyruvate or lactate as the substrate (Kaplan, 1965). Differences in the kinetic property of A, B and C-subunits must reflect amino acid substitutions which affect sites other than the active site of the polypeptide chain.