ABSTRACT
Uncompetitive inhibitio n result s w h e n a n inhibito r combines reversibl y wi th ES
to yiel d a n inactiv e E S I complex, E S + I * ± E S I , and K { = [ESI] / [ES][I] . T h e
double-reciprocal equatio n i s the n
where al l terms ar e the sam e a s in Equations (5.28) an d (5.29) . Graphica l analysi s
(Figure 5.9C ) shows a decreas e i n both K M and V m a x , resultin g i n line s paralle l t o
that give n i n the absenc e o f inhibitor . Uncompetitive inhibitor s may bind at a sit e
distant fro m th e activ e sit e o r a t a sit e differen t fro m bu t overlappin g wi t h th e
active site . I n either case , th e resul t is t o lowe r bot h th e catalyti c efficiency o f th e
enzyme an d it s apparen t bindin g efficienc y fo r th e substrate . Infinitel y hig h [S ]
wi l l no t conver t al l o f th e enzym e t o E S , and som e E S I wi l l a lway s b e present .
Uncompetitive inhibitio n i s commo n i n two-substrat e reaction s (se e below ) a n d
probably relate s t o th e sequentia l additio n o f tw o enzym e ligand s i n a n obligat e
order. I t is rar e i n single-substrat e reactions .
