Nucleic acid, proteins and enzymes (2).

Enzyme can be proteins or nucleic acids but mostly proteins. When protein enzymes are folded properly, their catalytic core will be collected together internally so as to make an isolated space for the contact between enzymes and substrates. Enzymes do not change during catalytic reaction but lower the energy threshold required for a reaction to happen. They make it by closing the distance between substrates.

The ability to hold substrates come from non-covalent bonds including hydrogen bonds,  electrostatic, and van der waals force. When the hydrophobic resides on an enzyme are held together, they form a catalytic core attacking one of the chemical bonds in the substrate and temporarily connected to the 'new' substrate to make it stable. Later, the enzyme will transfer this active bond to the other site, on the same substrate or other substrates and then release the new synthesized particles. By then, a reaction is catalyzed.