${\displaystyle {\ce {\overset {}{E->[{\ce {A \atop \downarrow }}]EA<=>E^{\ast }P->[{\ce {P \atop \uparrow }}]E^{\ast }->[{\ce {B \atop \downarrow }}]E^{\ast }B<=>EQ->[{\ce {Q \atop \uparrow }}]E}}}}$

In your article, replace the image with:

<chem>\overset{}{E ->[\ce{A \atop \downarrow}] EA <=> E^\ast P ->[\ce{P \atop \uparrow}] E^\ast ->[\ce{B \atop \downarrow}] E^\ast B <=> EQ ->[\ce{Q \atop \uparrow}] E}</chem>