Subject: What enzyme does Botox inhibit in a muscle contraction?

I recently read a newspaper article stating that Botox injections inhibited the 
production of an enzyme that causes muscle contraction.  I am unaware of an 
enzyme involved.  Could they be referring to Ach which acts as a 
neurotransmitter?  Did I miss something in my undergrad studies? :)

Thanks
sda

Re: What enzyme does Botox inhibit in a muscle contraction?