And the enzyme that basically catalyzes the addition of the phosphate group is known as protein kinases. So by adding our phosphate group onto our polypeptide chain, we're basically increasing the hydrophilic character of that protein. And as we'll see in a future lecture, this type of modification is usually used in the process of the cell cycle, in the cell growth process, as well as signal transduction. Now the second type of posttranslational modification is methylation. And methylation is basically the addition of a methyl group onto certain amino acids via the enzyme known as methyl transferase. So methylation usually increases the hydrophobic character of the enzyme.