Solutions For An Introduction to Medicinal Chemistry Chapter 2 Problem 6Q

The arrangements of amino acids within a protein, in which one residue is spatially linked to its neighbors forming alpha-helices, beta-pleated sheets, or beta-turns, are called the secondary structure of proteins. The three-dimensional shape of the proteins gives it a tertiary structure.

The arrangement of two or more subunits (separate polypeptide chains) with respect to each other in a more complex manner gives the quaternary structure of the protein. The secondary, tertiary and quaternary structure is formed mainly in order to minimize the unfavorable bonding interactions within or between the molecules and maximize the favorable interactions.

Figure: General phosphorylation reaction for proteins

Since the enzymes are proteins, thus the protein’s structure in an enzyme may vary from one enzyme to another. The tertiary structure of many enzymes is significantly altered by the phosphorylation of serine, threonine, or tyrosine residues.

The alcoholic group (-OH functional group) of the enzymes is involved in the phosphorylation. Thus, these play a very important role in signaling pathways within the cell. The tertiary structure of the protein is affected by phosphorylation for enhancing or retarding the activity of an enzyme (protein) within a cell.