TABLE 3.

Rate constants for proton transfer from various sites in human carbonic anhydrase II and site-specific mutants

Enzyme	Donor	Distance to Zn* (Å)		Reference
H64A	4-MI	4.8	Inhibitory	30
H64A-T200H	His-200	5.2	∼300	41
H64A-N67H	His-67	6.6	200	10
Wild-type	His-64	7.5	800	13
H64W	4-MI†	8.0	130	This work
H64A-N62H	His-62	8.2	∼30	10
H64A	4-MI‡	12.0	0	12

^*Distance between the zinc and N1 or N3 of the imidazole donor.

^†4-MI bound at Trp-64.

^‡4-MI bound at Trp-5.