kcatKm

1
Triosephosphate isomerase
Adenosine deaminase
Cytidine deaminase
Ketosteroid isomerase
Chorismate mutase
Cyclophylin
Carbonic Anhydrase
OMP Decarboxylase
Staph. nuclease
Catalytic Perfection
1010
108-109 M-1s-1
kcat/Km
(M-1s-1)
105
1
t1/21 min.
10-5
knon
(s-1)
10-10
OMP Decarboxylase The best enzyme known
t1/2106 years
10-15
Rate constants for nonenzymatic (knon) reactions
(bottom, blue squares) in units of s-1 and for
enzymatic (kcat/Km) reactions (top, red circles)
in units of M-1s-1 in neutral solution at 25 deg.
C. Enzyme proficiency ((kcat/Km)/knon) is
indicated by the length of the vertical bars.
From Science, vol 267, 90-93 (1995)