▁around ▁the ▁substr ate ▁in ▁a ▁manner ▁similar ▁to ▁other ▁en zym es ▁with ▁hydro ph ob ic ▁substr ates , ▁suggesting ▁this ▁fol d ▁is ▁characteristic ▁for ▁binding ▁hydro ph ob ic ▁substr ates . ▁ ▁No ▁complete ▁atomic ▁structure ▁of ▁K SI ▁appeared ▁until ▁ 1 9 9 7 , ▁when ▁an ▁N MR ▁structure ▁of ▁T I ▁K SI ▁was ▁reported . ▁This ▁structure ▁showed ▁that ▁the ▁active ▁site ▁is ▁a ▁deep ▁hydro ph ob ic ▁pit ▁with ▁Asp - 3 8 ▁and ▁T yr - 1 4 ▁located ▁at ▁the ▁bottom ▁of ▁this ▁pit . ▁The ▁structure ▁is ▁thus ▁entirely ▁consistent ▁with ▁the ▁proposed ▁mechan istic ▁roles ▁of ▁Asp - 3 8 ▁and ▁T yr - 1 4 . ▁ ▁As ▁of ▁late ▁ 2 0 0 7 , ▁ 2 5 ▁structures ▁have ▁been ▁solved ▁for ▁this ▁class ▁of ▁en zym es , ▁with ▁P DB ▁acc ession ▁codes ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁, ▁and ▁. ▁ ▁Mechan ism ▁▁ ▁K SI ▁catal y zes ▁the ▁re arr ang ement ▁of ▁a ▁carbon - car bon ▁double ▁bond ▁in ▁k et ost ero ids ▁through ▁an ▁en olate ▁intermediate ▁at ▁a ▁diffusion - limited ▁rate . ▁There ▁have ▁been ▁conflic ting ▁results ▁on ▁the ▁ion ization ▁state ▁of ▁the ▁intermediate , ▁whether ▁it ▁exists ▁as ▁the ▁en olate ▁or ▁en ol . ▁Pol lack ▁uses ▁a ▁therm od ynamic