ABSTRACT
The previous chapters described the kinetic treatments of enzyme. We learned how enzyme efficiently catalyzes the chemical reaction. Before 1980s, we had known from the dictionary and the textbook that the enzyme is composed of protein. However, the concept was denied when it was found that some RNAs have catalytic properties. Even though some RNAs are catalytic, most enzymes are composed of protein. From this chapter, we learn the way to understand the catalysis on the basis of the structure of enzyme. 6.1 Amino AcidsAmino acids are organic compounds. So, the “acid” means the organic acid, “carboxylic acid.” The amino nitrogen and carboxyl carbon are bound to the same carbon atom (Fig. 6.1). The structure shows that the carbon atom binds with four groups, amino and carboxyl groups, hydrogen atom, and R group. Thus, the central carbon binds with four different groups. Generally, the carbon atom bound to four different groups is called asymmetric or chiral carbon, and the carbon atom is in the center of tetrahedron, and four groups at its vertices. This leads to two tetrahedrons: the stereoisomers (they are not overlapped each other) (Fig. 6.2A).
