Table 2. Structural and biochemical effects of point mutations and the proposed roles of these residues.

Calcium occupancies are reported for both molecules in the asymmetric unit.

Mutation	Substrate bound?	Calcium 1 occupancy (%)	Calcium 2 occupancy (%)	Calcium 3 occupancy (%)	Remaining activity (%)	Proposed role
K108A	Yes	87/100	100/100	100/100	0	Catalytic base
E84A	No	0/0	0/0	100/86	0	Calcium 1/2 coordination
E39Q	Yes	75/83	63/69	100/100	6	Calcium 2 coordination
Q111A	Yes	89/65	100/99	100/100	1	Substrate binding, transition-state stabilization for the second part of the reaction
Q111N	Yes	76/86	96/100	98/100	8	Substrate binding, transition-state stabilization for the second part of the reaction
D107N	Yes	50/56	100/100	100/100	0	Calcium 1 coordination
R133A	Weakly	56/69	71/91	80/92	9	Substrate binding