What Is the Initial Step in the Mechanism of Fructose-1,6-Bisphosphate

Multiple Choice

What is the initial step in the mechanism of fructose-1,6-bisphosphate aldolase when the substrate is fructose-1,6-bisphosphate in its open-chain form?

A) attack of C-2 carbonyl group by the amine of lysine
B) deprotonation of C-3 hydroxyl by aspartate
C) protonation of C-2 carbonyl oxygen by histidine
D) attack of C-2 carbonyl group by the thiol of cysteine
E) none of the above