Table 1. Kinetic parameters of Diels—Alderase ribozymes.

Clone	Class	Km1 (diene), μM	Km2 (dienophile), μM	kcat, s-1	kcat/Km1, M-1 s-1	kcat/Km2, M-1 s-1	kcat/Km1Km2, M-2 s-1	Ki,* μM
49mer†	1	200 ± 35	5,200 ± 1,300	0.33 ± 0.06	1,667	64.1	3.2 × 105	11 (IC50)‡
49mer	1	148 ± 32	3,960 ± 623	0.32 ± 0.11	2,175	81.4	5.5 × 105	31.4 ± 1.8
F12	1	150 ± 32	1,650 ± 197	0.13 ± 0.04	878	79.9	5.3 × 105	29.3 ± 2.4
E12	1§	86 ± 10	7,890 ± 646	0.05 ± 0.02	583	6.4	7.4 × 104	57.3 ± 2.9
G11	2	396 ± 40	1,310 ± 65	0.01 ± 0.003	25	7.6	1.9 × 104	40.3 ± 9.4
E03	8	213 ± 7	6,150 ± 618	0.11 ± 0.04	504	17.5	8.2 × 104	68.0 ± 2.7

^*Measured with rac4 (Supporting Text) except ‡, where it was measured with the purified R,R-enantiomer of the reaction between 2 and N-pentylmaleimide (29).

^†As in refs. 29 (IC₅₀) and 33 (all other parameters).

^§Contains A15G change in internal loop sequence compared to 49mer and F12.