▁specific ity ▁since ▁it ▁is ▁the ▁initi ating ▁and ▁substr ate ▁recognition ▁domain . ▁ ▁In ▁one ▁example , ▁ad en yl ation ▁substr ate - binding ▁pocket ▁( defined ▁by ▁ 1 0 ▁resid ue ▁within ) ▁align ments ▁led ▁to ▁clusters ▁giving ▁rise ▁to ▁defined ▁specific ity ▁( i . e . ▁the ▁resid ues ▁of ▁the ▁en zym e ▁pocket ▁can ▁predict ▁non rib os om al ▁pe pt ide ▁sequence ). ▁ ▁In ▁sil ico ▁mut ations ▁of ▁substr ate - det erm ining ▁resid ues ▁also ▁led ▁to ▁varying ▁or ▁relax ed ▁specific ity . ▁ ▁Additionally , ▁the ▁NR PS ▁col linear ity ▁principle / rule ▁dict ates ▁that ▁given ▁the ▁order ▁of ▁ad en yl ation ▁domains ▁( and ▁substr ate - specific ity ▁code ) ▁throughout ▁the ▁NR PS ▁one ▁can ▁predict ▁the ▁am ino ▁acid ▁sequence ▁of ▁the ▁produced ▁small ▁pe pt ide . ▁ ▁NR PS , ▁NR PS - like ▁or ▁NR PS - P KS ▁complex es ▁also ▁exist ▁and ▁have ▁domain ▁variations , ▁add itions ▁and / or ▁exclus ions . ▁ ▁Support ing ▁examples ▁ ▁See ▁also ▁ ▁Non rib os om al ▁pe pt ide ▁ ▁Natural ▁product ▁ ▁Second ary ▁met abol ite ▁ ▁References ▁▁▁ ▁Mod ular ▁Pe pt ide ▁Syn th et ases ▁In vol ved ▁in ▁Non rib os om al ▁Pe pt ide ▁Syn thesis ▁ 1 9 9 7 ▁The ▁end ur ac id in ▁b ios yn th etic ▁gene ▁cluster