simply long-term structural changes in the brain to seeing memories as the products of "continuous enzymatic activity"

Long-term structural maintenance requires continuous enzymatic activity. For example, the average AMPA receptor lasts only around one day: http://www.ncbi.nlm.nih.gov/pubmed/18320299. The actin cytoskeleton, made up of molecules which largely specify the structure of synapses, also requires continuous remodeling. If a structure is visibly the same after vitrification (not trivial), that means the molecules specifying it are likely to not have changed much.