In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Simultaneous impairment of other enzymes in the BS biosynthetic pathways may contribute to overall effects of EE on BS synthesis .
### Output Text:
Simultaneous impairment of other enzymes in the <span class="chemical">BS</span> biosynthetic pathways may contribute to overall effects of <span class="chemical">EE</span> on <span class="chemical">BS</span> synthesis . 