Enzymes are effective protein catalysts for biochemical reactions. The
structural components of proteins are L-α-amino acids with the exception
of glycine, which is not chiral. The four levels of protein structure are primary,
secondary, tertiary, and quaternary structures. Primary structure is
related to the amino acid sequence. The amino group of one amino acid is
joined to the carboxyl group of the next amino acid by covalent bonding,
known as a peptide bond. The amino acid side-chain groups vary in terms
of their properties such as polarity, charge, and size. The polar amino acid
side groups tend to be on the outside of the protein where they interact
with water, whereas the hydrophobic groups tend to be in the interior part
of the protein. Secondary structure (α-helix, β-pleated sheet, and turns)
is important for protein conformation. Right-handed α-helix is a regular
arrangement of the polypeptide backbone by hydrogen bonding between
the carbonyl oxygen of one residue (i) and the nitrogenous proton of the
other residue (i+4). β-pleated sheet is a pleated structure composed of polypeptide
chains linked together through interamide hydrogen bonding
between adjacent strands of the sheet. Tertiary structure refers to the threedimensional
structure of folded protein. Presence of disulfide bridges,
hydrogen bonding, ionic bonding, and hydrophobic and van der Waals
interactions maintain the protein conformation. Folding the protein brings