v  V1
[S ]
[S ]H 1
[S ]H 1
[S ]H 2
 V1

V

V
2
2
[ S ]  K1
[ S ] H 1  K 2H 1
[ S ] H 1  K 2H 1
[ S ] H 2  K 3H 2
Terms used to define the production of -amyloid by -secretase (equation 5):
v = reaction rate
S = substrate
V1 = maximum reaction rate at low substrate concentrations
V2 = maximum reaction rate at high substrate concentrations
K1 = substrate affinity term at low substrate concentrations
K2 = substrate affinity term at high substrate concentrations
K3 = substrate affinity term at high substrate concentrations which produce inhibition
H1 = Hill coefficient used to define the substrate activation slope
H2 = Hill coefficient used to define the substrate inhibition slope
[ I ] Hx1
[ I ] Hx 2
[ I ] Hx 2
V1  V1  V1  V1is  Hx1
 V1  V1is  Hx 2
 V1  V1ii  Hx 2
1
[ I ]  K xHx
[ I ]  K xHx2 2
[ I ]  K xHx2 2
1
Terms used to define DAPT modification of the V1 term:
V1is =increase in reaction rate produced by low DAPT concentrations
V1ii =decrease in reaction rate produced by high DAPT concentrations
Kx1 = DAPT affinity binding term at low DAPT concentrations
Kx2 = DAPT affinity binding term at high DAPT concentrations
Hx1 = Hill coefficient used to define the DAPT activation slope
Hx2 = Hill coefficient used to define the DAPT inhibition slope
K1  K1  K1  K1is 
[ I ] Hx1
[ I ] Hx 2
[ I ] Hx 2





K

K

K

K
1
1is
1
1ii
[ I ] Hx1  K xHx1 1
[ I ] Hx 2  K xHx2 2
[ I ] Hx 2  K xHx2 2
Terms used to define DAPT modification of the K1 term:
K1is =change in substrate affinity term produced by low DAPT concentrations
K1ii = change in substrate affinity term produced by high DAPT concentrations
Kx1 , Kx2, Hx1 and Hx2 are the same as above.
[ I ] Hxx
V2  V2  V2  V2i  Hxx
[ I ]  K xxHxx
1
Terms used to define DAPT modification of the V2 term:
V2i = decrease in reaction rate produced by DAPT
Kxx1 = DAPT affinity binding term
Hxx = Hill coefficient used to define the DAPT inhibition slope
[ I ] Hxx
K 2  K 2  K 2  K 2i  Hxx
[ I ]  K xxHxx
1
Terms used to define DAPT modification of the K2 term:
K2i = change in substrate affinity term produced by DAPT concentrations
Kxx1 and Hxx are the same as above.