The sulfhydryl (thiol) group (SH) of cysteine is responsible for the chemical properties of the whole GSH molecule (L-gamma-glutamyl-Lcysteinylglycine).
Both the filtrate and the dialyzate of agave pollen can activate the enzyme, thus proving that there was activating substance of the thiol group in agave pollen.
So the UV has enough energy to where it'll knock nitric oxide down to a cysteine thiol and protein, and then the UV spectrum will release nitric oxide down the metals.