I need to know any flaws there are in the lock and key theory of enzymes. Also what is the transition state of an enzyme?

Most enzymes are complex , globular proteins made up of one or more polypetides chains... first... a mspecific substrate molecule arrives at the active site of the enzyme molecule... 2nd ... the substrate molecule binds to the acttive site to form an enymes-substrate complex which is very unstable... then... product molecules have the active site of the enzymes