What directly hydrolyzes cGMP during phototransduction?

During phototransduction, phosphodiesterase 6 (PDE6) plays a critical role in the cascade of biochemical events that occur in response to light. When photons strike rhodopsin, it undergoes a conformational change to form metarhodopsin II, which then activates the G-protein transducin. The activated transducin subsequently activates PDE6.

PDE6 directly hydrolyzes cyclic guanosine monophosphate (cGMP) to guanosine monophosphate (GMP), leading to a decrease in cGMP levels in the photoreceptor cells. This reduction in cGMP concentration causes the closure of cGMP-gated sodium channels in the photoreceptor cell membrane, resulting in hyperpolarization of the cell and ultimately contributing to the transmission of visual signals to the brain.

Understanding the exact role of PDE6 in this process highlights its significance in the phototransduction pathway, making it a crucial enzyme for vision.