50 Fun Facts About Enzymes

Taq polymerase, the heat-proof enzyme behind PCR, came from bacteria found in which national park?

Yellowstone's Mushroom Spring gave science Thermus aquaticus, whose enzyme survives 95 °C. That let PCR copy DNA through repeated heating without fresh enzyme being added for every cycle.

Adults who cannot digest the sugar in milk make too little of which enzyme in the small intestine?

Lactase splits milk sugar into two simpler sugars that the gut can absorb. In most of the world's population, the body makes far less of it after weaning.

Which painkiller, first sold by Bayer, permanently disables the COX enzymes that make prostaglandins?

Aspirin shuts the enzyme down for good, while ibuprofen only blocks it for a while. In platelets the block lasts for the cell's whole life of 8 to 9 days, which is why a small daily dose reduces clotting.

PETase, an enzyme from bacteria found near a Japanese recycling site, breaks down which material?

Plastic of the PET type, used in drinks bottles, is what PETase cuts apart. The bacteria that make it were found in sludge and can feed on the carbon in the bottles.

Many meat tenderizers get their protein-cutting enzyme from the latex of which tropical fruit?

Papaya latex is dried to make papain, the active ingredient in many commercial tenderizers. People who are allergic to latex may react to the fruit and its enzyme too.

Which model by Emil Fischer pictures a substrate fitting an enzyme's exactly matching pocket?

Lock and key was Fischer's image for why each enzyme accepts only its own substrate. Later work added flexibility: in the induced fit version, the pocket reshapes itself as the substrate binds.

Which mix of enzymes, traditionally taken from the stomachs of calves, curdles milk in cheesemaking?

Rennet contains chymosin, which curdles the casein proteins in milk. Each ruminant makes its own version, so kid goat rennet is sold for goat's milk and lamb rennet for sheep's milk.

Which enzyme in saliva starts digesting starch, so that rice tastes sweeter the longer it is chewed?

Amylase begins cutting starch into sugar before food is even swallowed. Some historic brewers relied on it, chewing grain so that their saliva would start the conversion.

Enzymes speed up reactions by lowering which barrier that reacting molecules must first overcome?

Activation energy is the push a reaction needs to get going, and enzymes often cut it enough to speed things up millions of times. The enzyme itself is not consumed, so it can work again and again.

Raised levels of the enzymes ALT and AST in a blood test usually point to damage in which organ?

Liver injury of almost any kind raises ALT, so doctors read the pair as markers of damage there. AST is the less specific of the two, because a variety of other tissues can release it.

Which protein-digesting stomach enzyme is most active in strong acid, at around pH 2?

Pepsin is released as inactive pepsinogen and only switches on when it meets the stomach's hydrochloric acid. Theodor Schwann, who discovered it, named it after the Greek word for digestion.

Which process, which also hardens a boiled egg, wrecks an enzyme's shape when it overheats?

Denaturation unravels the folded chain, so the enzyme's working pocket no longer fits its substrate. Strong acid, alcohol and radiation can do the same job as heat.

Which class of cholesterol-lowering drugs works by blocking the enzyme HMG-CoA reductase?

Statins jam the enzyme at the center of the body's own cholesterol production. Natural versions are made by fungi, probably as a weapon against the microbes they compete with.

Test strips used by people with diabetes carry an oxidase enzyme that reacts with which sugar?

Glucose oxidase pulls electrons from the sugar, producing a current in proportion to how much is there. Honeybees put the same enzyme into honey, where it acts as a natural preservative.

Most enzymes in the human body work fastest near which temperature, slowing sharply above it?

37 °C is the average human body temperature, and the body's enzymes are tuned to work best close to it. Above 40 °C they quickly start to lose their shape.

Subtilisin, a protein-digesting bacterial enzyme, is made in bulk to cut stains in which product?

Laundry detergent uses it to break down protein stains such as blood and egg. Makers re-engineer the enzyme first, because the natural form is easily knocked out by detergents and heat.

The induced fit model likens an enzyme reshaping around its substrate to which item being put on?

A glove changes shape as a hand slides in, just as the enzyme's pocket shifts when its substrate arrives. Daniel Koshland proposed the idea in 1958 as a more flexible update of an older, rigid picture.

Which digestive fluid, stored in the gallbladder, breaks fat into droplets for enzymes to attack?

Bile works like a soap, coating fat droplets so that they cannot merge back together. The far larger surface area lets fat-splitting enzymes from the pancreas get to work.

ACE inhibitors, first modelled on a peptide in pit viper venom, are prescribed mainly to lower what?

Blood pressure falls because the drugs block angiotensin-converting enzyme, which lets blood vessels relax. The snake's venom works the same way, by severely depressing blood pressure.

Most enzymes are proteins, long folded chains built from which small molecules in a set order?

Amino acids in their exact sequence decide how the chain folds, and the fold decides what the enzyme can do. Yet only around two to four of them usually carry out the actual chemistry.

Which enzyme from the pancreas digests fats by cutting fatty acids off triglyceride molecules?

Lipase uses water to clip the fatty acids from fat molecules. Related enzymes do very different jobs elsewhere in the body, including helping to build fat-based hormones.

Humans cannot digest the fiber in grass and paper because the body makes no version of which enzyme?

Cellulase is missing in most animals, and even cattle and sheep rely on gut bacteria to make it for them. The textile industry uses the enzyme for the 'biostoning' of jeans.

Which mold-derived antibiotic kills bacteria by jamming the enzymes that cross-link their cell walls?

Penicillin stops a growing bacterium from completing its wall. The enzymes it disables are named after the drug itself: biochemists call them penicillin-binding proteins.

Which enzyme, found in nearly all oxygen-exposed life, splits hydrogen peroxide into water and oxygen?

Catalase is among the fastest enzymes known, with one molecule breaking down millions of hydrogen peroxide molecules each second. Labs test bacteria for it by watching for oxygen bubbles.

Which enzyme makes fireflies glow by oxidizing a light-emitting compound, using oxygen and ATP?

Luciferase also lights up click beetles. Because its reaction needs ATP, laboratories use the firefly enzyme widely in biotechnology.

Which fast-acting poison kills by blocking cytochrome c oxidase, the enzyme that lets cells use oxygen?

Cyanide leaves the body's tissues unable to use oxygen, however much is carried in the blood. Because that oxygen stays in the veins, a victim's skin can turn cherry red.

Which enzyme unzips DNA ahead of copying by breaking the hydrogen bonds between its two strands?

Helicase is a motor protein that burns ATP as it travels along the DNA, prising the strands apart. Cells make many kinds, since copying, reading and repairing DNA all need the strands separated.

Which molecular scissors, such as EcoRI, do bacteria use on viral DNA and labs use for gene splicing?

Restriction enzymes each recognize a specific short stretch of DNA and cut there. The name comes from studies of a virus whose growth was restricted inside certain host bacteria.

Which enzyme does the cutting in CRISPR gene editing, steered to its DNA target by a guide RNA?

Cas9 is part of an immune system that bacteria use against viruses. In 2012 Jennifer Doudna and Emmanuelle Charpentier showed that a single guide RNA could aim it at chosen DNA sequences.

Which enzyme, the most abundant on Earth, grabs carbon dioxide from the air during photosynthesis?

Rubisco accounts for about half the soluble protein in the leaves of many plants. It is far from perfect, sometimes reacting with oxygen instead of carbon dioxide.

Which type of enzyme inhibition can be overcome simply by adding more substrate to the reaction?

Competitive inhibitors vie with the substrate for the enzyme, so extra substrate crowds them out. Medicine exploits this: ethanol is sometimes given after methanol is swallowed, to keep the enzyme too busy to process the poison.

Which term describes control of an enzyme by a molecule binding away from its active site?

Allosteric regulators work at a distance: binding at a second site changes the protein's shape. That can boost the enzyme's activity as well as curb it.

In which kind of control does a pathway's end product slow an enzyme near the start of that pathway?

Negative feedback means the end product regulates its own supply, slowing the line once enough has been made. The enzyme it targets is usually the pathway's first irreversible step.

What are inactive enzyme precursors called, like those the pancreas makes to avoid digesting itself?

Zymogens stay harmless until they are safely clear of the cells that made them. Most of the proteins that clot blood circulate in the same switched-off form.

What are RNA molecules that act as enzymes called, a find that won Cech and Altman a Nobel Prize?

Ribozymes overturned the rule that every enzyme is a protein. The best known sits inside the ribosome, where RNA itself forges the links that build every protein.

Which family of about 500 human enzymes transfers phosphate groups from ATP onto other molecules?

Kinases are used throughout the cell to pass on signals. They are easily confused with phosphatases, which do the opposite job and strip phosphate groups off again.

Which class of enzymes, numbered EC 3 by the Enzyme Commission, breaks chemical bonds by adding water?

Hydrolases include the enzymes that digest food, which cut fats and starches apart with water. The Enzyme Commission sorts every known enzyme into seven such top-level classes.

What name is given to the point where adding more substrate no longer speeds up an enzyme reaction?

Saturation means every enzyme molecule is already occupied by substrate, so the reaction runs at its maximum rate. Biochemists label that ceiling Vmax.

Which B vitamin does the body build into NAD, a coenzyme that carries electrons between reactions?

Niacin, also known as vitamin B3, matters so much that a diet lacking it causes pellagra, a disease marked by inflamed skin, diarrhea and dementia.

Nerve agents such as sarin kill by blocking which enzyme that clears signals at nerve junctions?

Acetylcholinesterase normally clears the signal so that a muscle can relax. With the enzyme blocked, victims lose control of the muscles they need for breathing.

Which bacteria-killing enzyme in tears and egg white did Alexander Fleming discover in nasal mucus?

Lysozyme bursts bacteria by breaking down the material that holds their cell walls together. Fleming showed the germ-killing power of mucus in 1922 and coined the enzyme's name himself.

Which zinc-containing enzyme in red blood cells converts carbon dioxide into bicarbonate for transport?

Carbonic anhydrase lets blood carry carbon dioxide as dissolved bicarbonate, then helps release the gas again in the lungs. The same reaction helps keep the blood's pH steady.

Which enzyme in mitochondria works as a rotary motor, spun by a flow of protons?

ATP synthase has parts that physically rotate as protons cross the membrane. Working out how it turns earned Paul Boyer and John Walker a share of the 1997 Nobel Prize in Chemistry.

Which enzyme, discovered by Howard Temin and David Baltimore, lets HIV copy its RNA genome into DNA?

Reverse transcriptase copies information from RNA into DNA, the opposite of the usual direction. Its discovery in 1970 earned Temin and Baltimore a share of the 1975 Nobel Prize in Physiology or Medicine.

Which enzyme, active in most cancer cells, rebuilds the protective caps on the ends of chromosomes?

Telomerase is normally absent from most body cells but active in egg and sperm cells. Elizabeth Blackburn, Carol Greider and Jack Szostak were awarded a 2009 Nobel Prize for the discovery.

Which German chemist won a Nobel Prize for proving that fermentation needs no living yeast cells?

Eduard Buchner found that yeast extracts still fermented sugar when no living cells were left in the mixture. He named the enzyme responsible zymase and received the 1907 Nobel Prize in Chemistry.

Which enzyme did James Sumner crystallize from jack beans, first showing that an enzyme is a protein?

Urease was the first enzyme ever crystallized. Many of Sumner's colleagues had thought the feat impossible, but it brought him a share of the 1946 Nobel Prize in Chemistry.

Which starch-digesting enzyme, extracted from malt by Anselme Payen, was the first ever discovered?

Diastase left a mark on every enzyme named since: its ending became the -ase suffix. Payen and his colleague Jean-François Persoz found it in 1833 while working at a French sugar factory.

Which Canadian physician co-wrote a landmark paper on enzyme reaction rates with Leonor Michaelis?

Maud Menten was among the first women in Canada to earn a medical doctorate. Her 1913 work with Michaelis in Berlin produced the rate equation that still carries both their names.

Which double-reciprocal graph turns enzyme rate data into a straight line for estimating Vmax?

The Lineweaver–Burk plot graphs one over the rate against one over the substrate concentration. Its drawback is that it distorts the errors in the data, so it is not the most accurate way to find an enzyme's constants.