Proteins as enzymes
	There are 6 major classes of enzymes:     1.Oxidoreductases, which are involved in oxidation, reduction, and electron or proton transfer reactions;    2.Transferases, catalyzing reactions in which groups are transferred;    3.Hydrolases that cleave various covalent bonds by hydrolysis;    4.Lyases catalyze reactions forming or breaking double bonds;    5.Isomerases catalyze isomerization reactions;    6.Ligases join constituents together covalently.