A comparative study of human muscle and brain creatine kinases expressed in Escherichia coli

We report the expression of the human muscle (CK-MM) and brain (CK-BB) crea tine kinases in Escherichia coli. The proteins have been purified to appare nt homogeneity and several of their physical and kinetic properties investi gated. In the process, we have conclusively verified the correct DNA sequen ce of the genes encoding the respective isozymes, and determined the correc t primary structure and mass of the gene products, alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other , and no obvious gross structural differences. However, Western blot analys es demonstrated the general lack of antigenic cross-reactivity between thes e isozymes. Preliminary kinetic analyses show the K-m and k(cat) values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CK s do not, however, exhibit the synergism of substrate binding that is obser ved, for example, in rabbit muscle creatine kinase.