Biology.SE has a similar discussion but it would be good to define it here. What types of biochemistry questions are suitable for Chemistry.SE and at what point does it become a question that should be migrated to Biology.SE?
I propose this model.
If the question is related to chemistry aspect, it will be part of Chemistry SE, where a chemist can easily understand / answer the question.
Whereas if the question is related to biological function / activity, then it will be shunted to biology SE.
In the tricky situation, If the question is on relation between chemistry and biology, then the author of the question is expected to clarify which part of the question s/he is more comfortable / expecting answers; and accordingly it goes to respective SE.