Enzymes y uncatalyzed omp decarboxylation has a half-time of 78 million years, while catalyzed omp-enzyme decarboxylation has a half-time of 20 milliseconds y enzymes increase the rate of a spontaneous reaction by 1012 1020 times. Fundamentally, reactions need to go faster y enzymes enable you to increase the rate of reaction without increasing temperature evolutionary advantage. Enzyme structure y enzymes are proteins, products of genes y enzymes are usually large and the substrate is usually very small y the substrate only interacts with a specific region of the enzyme called the active site y. No, the active site is only apparent when you acquire the correct conformation when the enzyme folds to the correct native conformation, that is when the active site becomes apparent. In vitro, the rate of catalysis can be measured by measuring the rate at which the substrate disappears or the rate at which the product is made.