I only know of a few enzymes shared between us and our plants (I haven't had
biochem yet!). But as all life forms on this planet share at least one
biochemical pathway (glycolysis), I assume that the enzymes involved are
identical. Of course this all depends on your definition of life. (Is a virus
alive?)
The end products may not be the same, but we do share too many biochemical
pathways to not be 'related'.
JMS