Viagra and Phosphodiesterase 5 Complex

Human phosphodiesterase 5 (PDE5) is the protein that viagra binds to and inhits. Viagra has no direct relaxant effect that leads to penile erection but it enhances the effect of nitric oxide (NO) by inhibiting PDE5. PDE5 is responsible for the degradation of cyclic GMP (cGMP) in the penile corpus cavernosum. When sexual stimulus leads to an increase in cGMP levels, smooth muscles relax allowing for blood to flow into the penis. This piece illustrates the enzyme, PDE5, in a novel box-type ribbon diagram, with a smooth gradient over the length of the protein polypeptide chain. Viagra itself is shown as space-filling cartoon-type spheres.

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