What characteristics do all enzymes share?

Hint: Enzymes are proteinaceous compounds that act as biological catalysts in cellular reactions. Catalysts serve the purpose of increasing the speed of a chemical reaction.

Complete answer:
More than 4000 biological reactions are catalyzed by enzymes present in several organisms. Enzymes also exist in other forms like catalytic RNA molecules called ribozymes which also carry out biological reactions in the cells. The specificity of enzymes comes from the unique three dimensional structure of enzymes. The reactivity of enzymes for biological reactions is increased by lowering the activation of energy of the enzymes. The activity of some enzymes leads to an increase in the rate of a reaction by a million times.
Enzymes act like general catalysts and do not interfere in their concerned biological reaction. Enzymes also do not alter the state of equilibrium of the reaction. Enzymes have a specific substrate and differ with regular catalysts in this characteristic. Enzymatic activity can be affected by the interference of other molecules. Molecules that increase the activity of the enzyme are called activators and the molecules that decrease the activity of the enzyme are called inhibitors.
Some enzymes exhibit pseudo catalytic properties as they are unable to perform enzyme catalysis. This inability to carry out biological catalysis is reflected in the amino acid sequences of the enzyme.

Note:
The molecules on which enzymes act on are called substrate molecules. The enzymes facilitate the conversion of these substrate molecules into different molecules called product molecules. Almost all biological metabolic reactions require the presence of enzymes to progress efficiently. Enzyme catalysis is required for the sustenance of life.