An enzyme is an organic catalyst, and usually a protein, that exists within an organism for the purpose of accelerating a specific chemical reaction within it. Like all catalysts, enzymes are not consumed or permanently altered during the process of catalyzing reactions.
Enzyme molecules have extremely complex structures, largely as a result of their long evolutionary history. The number of different enzymes that exist is vast and unknown, in part because each species can have its own set of thousands of enzymes, and there are variations even within the same species. For example, a single species of bacteria may contain hundreds to more than a thousand different enzymes, depending on its species, its metabolic capabilities and its evolutionary history. A human body contains roughly 75,000 different enzymes, and a typical human cell may contain more than a thousand.
All living things require enzymes, and they play crucial roles in numerous processes, including metabolism, digestion, and cellular regulation. A few examples among human enzymes include amylase, which is found in saliva and pancreatic juice and breaks down starch into smaller sugar molecules, alcohol dehydrogenase, which helps metabolize alcohol in the liver, and DNA polymerase, which is involved in DNA replication and repair.
Several dozen enzymes are manufactured on a large scale. A major area of applications is for use as drugs, in disease diagnosis, and in drug manufacturing. Enzymes can have important advantages over conventional drugs in some situations, including the ability to target specific molecules or reactions with high precision, thereby resulting in greater efficiency and fewer side effects. Also, because they are proteins, enzymes are naturally biodegradable, thus minimizing environmental effects and possible toxicity. Other major categories of applications for enzymes include the production of foodstuffs, biofuels, textiles and fertilizers.
Most enzymes used by the pharmaceutical industry are obtained from microbial sources, especially bacteria, fungi and yeasts, through fermentation and recombinant DNA technology. While enzymes can also be sourced from plants and animals, microbial enzymes can offer advantages in terms of production efficiency, purity, and the ability to obtain highly specific properties. This makes them the predominant source for many medical and pharmaceutical applications.
Environmental degradation and the consequent loss of animal and plant diversity can, of course, negatively affect the discovery of new animal and plant substances to use as pharmaceuticals and in pharmaceutical manufacturing. But it can also further reduce the chances of discovering new enzymes because many microorganism species, with their unique enzymes, live in symbiosis with specific plant and animal species, and thus the loss of host species can lead to the loss of microbial species.