In others there may be excessive activity of certain enzymes. Measurements of the activity of certain enzymes in the blood plasma, red blood cells, or tissue samples are important in diagnosing disease.
Enzymes are important in the chemical industry, in food processing, in agriculture, and in the home.
Classification - There are about 2000 different enzymes identified to date and they are classified on the basis of the reactions which they catalyze by an International Classification of Enzymes. In the early 1800s suggestions were made of some form of catalysis in digestion of meat by secretions of the stomach or conversion of starch into sugar by saliva or plant extracts. In 1897 the Buchner brothers succeeded in producing extracts in soluble form, from yeast cells, that were capable of carrying out ethanol fermentation. Finally, in 1926 James Sumner isolated and purified the enzyme urease from jack beans. He found that this enzyme consisted entirely of protein and postulated that all enzymes would consist of proteins.