Enzymes with kcat/Km values close to diffusion controlled (108 - 109 M-1s-1)
enzyme	substrate	kcat (s-1)	Km (M)	kcat/Km (M-1s-1)
acetylcholinesterase	acetylcholine	1.4 x 104	9 x 10-5	1.6 x 108
carbonic anhydrase	CO2	1 x 106	1.2 x 10-2	8.3 x 107
	HCO3-	4 x 105	2.6 x 10-2	1.5 x 107
catalase	H2O2	4 x 107	1.1	4 x 107
crotonase	crotonyl-CoA	5.7 x 103	2 x 10-5	2.8 x 108
fumarase	fumarate	8 x 102	5 x 10-6	1.6 x 108
	malate	9 x 102	2.5 x 10-5	3.6 x 107
triose phosphate isomeraser	glyceraldehyde-3-P	4.3 x 103	4.7 x 10-4	2.4 x 108
b-lactamase	benzylpenicillin	2.0 x 103	2 x 10-4	1 x 108