An important element in human chemistry, an enzyme is a protein manufactured by a cell, and is a catalyst in various biological functions. For example, enzymes help break down larger molecules of starch, fat, and protein during digestion.

The word enzyme was coined by a German physiologist in the late 1800s to name a digestive process that scientists had been observing. The word was later given to the actual agents discovered to spark the reactions, taken from the Greek énzymos, which meant "leavened." (Leavening makes bread rise.) Remember that the word enzyme is spelled with a y and not an i, which makes sense, since when scientists observe chemical processes, they often ask "why?"

Definitions of enzyme

n any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions

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ADA, adenosine deaminase
an enzyme found in mammals that can catalyze the deamination of adenosine into inosine and ammonia
any of a group of proteins found in saliva and pancreatic juice and parts of plants; help convert starch to sugar
an enzyme that hydrolyses acetylcholine (into choline and acetic acid)
an enzyme that induces coagulation
any enzyme that catalyzes the hydrolysis of collagen and gelatin
one of a series of enzymes in the blood serum that are part of the immune response
enzyme found in most plant and animal cells that functions as an oxidative catalyst; decomposes hydrogen peroxide into oxygen and water
Cox, cyclooxygenase
either of two related enzymes that control the production of prostaglandins and are blocked by aspirin
any of the enzymes that hydrolize the carboxyl group
an enzyme that removes the iodine radical
an enzyme that catalyzes the hydrolysis of disaccharides into monosaccharides
a pancreatic enzyme that catalyzes the hydrolysis of elastin
enzyme in the intestinal juice that converts inactive trypsinogen into active trypsin
enzyme that acts as a catalyst in converting histidine to histamine
Hyazyme, hyaluronidase, spreading factor
an enzyme (trade name Hyazyme) that splits hyaluronic acid and so lowers its viscosity and increases the permeability of connective tissue and the absorption of fluids
an enzyme that catalyzes its substrate to an isomeric form
an enzyme that catalyzes the conversion of a proenzyme to an active enzyme
an enzyme secreted in the digestive tract that catalyzes the breakdown of fats into individual fatty acids that can be absorbed into the bloodstream
lysozyme, muramidase
an enzyme found in saliva and sweat and tears that destroys the cell walls of certain bacteria
MAO, monoamine oxidase
an enzyme that catalyzes the oxidation of many body compounds (e.g., epinephrine and norepinephrine and serotonin)
an enzyme of nitrogen-fixing microorganisms that catalyzes the conversion of nitrogen to ammonia
general term for enzymes that catalyze the hydrolysis of nucleic acid by cleaving chains of nucleotides into smaller units
any of the enzymes that catalyze biological oxidation
an enzyme that catalyzes oxidation-reduction
a proteolytic enzyme obtained from the unripe papaya; used as a meat tenderizer
beta-lactamase, penicillinase
enzyme produced by certain bacteria that inactivates penicillin and results in resistance to that antibiotic
an enzyme produced in the stomach that splits proteins into peptones
precursor of pepsin; stored in the stomach walls and converted to pepsin by hydrochloric acid in the stomach
any of a group of enzymes that act as a catalyst in the hydrolysis of organic phosphates
fibrinolysin, plasmin
an enzyme that dissolves the fibrin of blood clots
an enzyme that catalyzes the formation of new DNA and RNA from an existing strand of DNA or RNA
peptidase, protease, proteinase, proteolytic enzyme
any enzyme that catalyzes the splitting of proteins into smaller peptide fractions and amino acids by a process known as proteolysis
an enzyme that catalyses the biochemical reduction of some specified substance
chymosin, rennin
an enzyme that occurs in gastric juice; causes milk to coagulate
a set of enzymes believed to snip pieces off a longer protein producing fragments of amyloid protein that bunch up and create amyloid protein plaques in brain tissue (the pathological hallmark of Alzheimer's)
an enzyme produced by some hemolytic strains of streptococcus that dissolves fibrinous secretions from infections; used medicinally (often in combination with streptokinase)
an enzyme produced by some strains of streptococcus that can liquefy blood clots by converting plasminogen to plasmin; used medicinally in some cases of myocardial infarction and pulmonary embolism
SOD, superoxide dismutase
an enzyme that catalyzes the conversion of superoxide into hydrogen peroxide and oxygen
an enzyme in eukaryotic cells that can add telomeres to the ends of chromosomes after they divide
any of various enzymes that move a chemical group from one compound to another compound
an enzyme of pancreatic origin; catalyzes the hydrolysis of proteins to smaller polypeptide units
an enzyme that catalyzes the hydrolysis of urea into carbon dioxide and ammonia; is present in intestinal bacteria
a complex of enzymes that cause glycolysis; originally found in yeast but also present in higher organisms
a nuclease that cleaves nucleic acids at interior bonds and so produces fragments of various sizes
a nuclease that releases one nucleotide at a time (serially) beginning at one of a nucleic acid
5-hydroxy-3-methylglutaryl-coenzyme A reductase, HMG-CoA reductase
a liver enzyme that is responsible for producing cholesterol
any of a group of proteases that mediate apoptosis
ACE, angiotensin converting enzyme, angiotensin-converting enzyme
proteolytic enzyme that converts angiotensin I into angiotensin II
an enzyme that acts on fibrinogen in blood causing it to clot
Cox-1, cyclooxygenase-1
an enzyme that regulates prostaglandins that are important for the health of the stomach lining and kidneys
Cox-2, cyclooxygenase-2
an enzyme that makes prostaglandins that cause inflammation and pain and fever
an amylase secreted in saliva
RNase, ribonuclease, ribonucleinase
a transferase that catalyzes the hydrolysis of ribonucleic acid
invertase, saccharase, sucrase
an enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose
Lactaid, lactase
any of a group of enzymes (trade name Lactaid) that hydrolyze lactose to glucose and galactose
an oxidoreductase that catalyzes the incorporation of molecular oxygen
any of a group of enzymes (occurring especially in plant cells) that catalyze the oxidation of a compound by a peroxide
an inactive form of plasmin that occurs in plasma and is converted to plasmin by organic solvents
plasminogen activator, urokinase
protease produced in the kidney that converts plasminogen to plasmin and so initiates fibrinolysis
DNA polymerase
the enzyme responsible for DNA replication
RNA polymerase, transcriptase
the enzyme that copies DNA into RNA
reverse transcriptase
a polymerase that catalyzes the formation of DNA using RNA as a template; found especially in retroviruses
a proteolytic enzyme secreted by the kidneys; catalyzes the formation of angiotensin and thus affects blood pressure
chymosin, rennin
an enzyme that occurs in gastric juice; causes milk to coagulate
aminopherase, aminotransferase, transaminase
a class of transferases that catalyze transamination (that transfer an amino group from an amino acid to another compound)
inactive precursor of trypsin; a substance secreted by the pancreas and converted to active trypsin by enterokinase in the small intestine
Type of:
accelerator, catalyst
(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected
any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes

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