👉 In biochemistry, a phosphodiesterase is an enzyme that catalyzes the hydrolysis of phosphodiester bonds. These bonds are responsible for the physiological functions of sexual and reproductive systems. The main function of phosphodiesterases is to regulate the flow of energy in cells by breaking down or increasing the concentration of certain hormones, such as testosterone and estrogen. Phosphodiesterase enzymes can be found in a wide variety of tissues, including muscle, heart, liver, brain,