Enzymes
the cell's chemists
Enzymes perform all of the basic chemical tasks needed to sustain life. Each binds to its target molecule, performs a chemical change, and then releases the altered molecule. Atomic structures have revealed the atomic-level details of how enzymes work to recognize their substrates and catalyze their chemical reactions.
Molecule of the Month Articles (63)
 | AAA+ Proteases AAA+ proteases are ATP-powered molecular motors that thread protein chains through a hole |
 | ABO Blood Type Glycosyltransferases ABO blood types are determined by an enzyme that attaches sugars to proteins |
 | Acetylcholinesterase Acetylcholinesterase stops the signal between a nerve cell and a muscle cell |
 | Aconitase and Iron Regulatory Protein 1 Aconitase performs a reaction in the citric acid cycle, and moonlights as a regulatory protein |
 | Alcohol Dehydrogenase Alcohol dehydrogenase detoxifies the ethanol we drink |
 | Alpha-amylase Amylases digest starch to produce glucose |
 | Aminoacyl-tRNA Synthetases Aminoacyl-tRNA synthetases ensure that the proper amino acids are used to build proteins |
 | Anabolic Steroids Anabolic steroids like testosterone are among the most common performance enhancing drugs |
 | Beta-galactosidase Beta-galactosidase is a powerful tool for genetic engineering of bacteria |
 | Beta-secretase Beta-secretase trims proteins in the cell and plays an important role in Alzheimer's disease |
 | cAMP-dependent Protein Kinase (PKA) PKA delivers cellular signals by adding phosphates to proteins |
 | Carbonic Anhydrase Carbonic anhydrase solubilizes carbon dioxide gas so we can breathe it out |
 | Carotenoid Oxygenase Light-sensing retinal molecules are built from colorful carotenoids in our diet |
 | Caspases Caspases disassemble proteins during the process of programmed cell death |
 | Catalase Catalase protects us from dangerous reactive oxidizing molecules |
 | Citrate Synthase Citrate synthase opens and closes around its substrates as part of the citric acid cycle |
 | Citric Acid Cycle Eight enzymes form a cyclic pathway for energy production and biosynthesis |
 | Cyclooxygenase Aspirin attacks an important enzyme in pain signaling and blood clotting |
 | Cytochrome p450 Cytochrome p450 detoxifies and solubilizes drugs and poisons by modifying them with oxygen |
 | Dihydrofolate Reductase DHFR is a target for cancer chemotherapy and bacterial infection |
 | DNA Ligase DNA ligase reconnects broken DNA strands, and is used to engineer recombinant DNA |
 | Exosomes Exosomes destroy messenger RNA molecules after they have finished their jobs |
 | Fatty Acid Synthase Fatty acids are constructed in many sequential steps by a large protein complex |
 | Glucansucrase Bacteria adhere to our teeth by building sticky sugar chains |
 | Glucose Oxidase Glucose oxidase measures blood glucose level in biosensors |
 | Glutamine Synthetase Glutamine synthetase monitors the levels of nitrogen-rich amino acids and decides when to make more |
 | Glycogen Phosphorylase Glycogen phosphorylase releases sugar from its cellular storehouse |
 | Glycolytic Enzymes The ten enzymes of glycolysis break down sugar in our diet |
 | HIV Reverse Transcriptase HIV builds a DNA copy of its RNA genome, providing a unique target for drug therapy |
 | Hydrogenase Hydrogenases use unusual metal ions to split hydrogen gas |
 | Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) Cells salvage and recycle their obsolete DNA and RNA |
 | Isocitrate Dehydrogenase Atomic structures have revealed the catalytic steps of a citric acid cycle enzyme |
 | Lactate Dehydrogenase Our cells temporarily build lactate when supplies of oxygen are low |
 | Luciferase Organisms from fireflies to bacteria use luciferase to emit light |
 | Lysozyme Lysozyme attacks the cell walls of bacteria |
 | Methyl-coenzyme M Reductase Methanogens use sophisticated molecular tools to build methane |
 | New Delhi Metallo-Beta-Lactamase Antibiotics can save lives, but antibiotic-resistant strains of bacteria pose a dangerous threat |
 | Nitrogenase Nitrogenase uses an exotic cluster of metals to fix atmospheric nitrogen into bioavailable ammonia |
 | O-GlcNAc Transferase Some protein functions are regulated when sugars are attached |
 | Oxidosqualene Cyclase Oxidosqualine cyclase forms the unusual fused rings of cholesterol molecules |
 | Pepsin Pepsin digests proteins in strong stomach acid |
 | Phenylalanine Hydroxylase An unusual cofactor is used in the synthesis of aromatic amino acids |
 | Poly(A) Polymerase Poly(A) polymerase adds a long tail of adenine nucleotides at the end of messenger RNA |
 | Pyruvate Dehydrogenase Complex A huge molecular complex links three sequential reactions for energy production |
 | Restriction Enzymes Bacterial enzymes that cut DNA are useful tools for genetic engineering |
 | Rhomboid Protease GlpG Some proteases cut proteins embedded in cell membranes |
 | Ribonuclease A Ribonuclease cuts and controls RNA |
 | Ribosome Ribosomes are complex molecular machines that build proteins |
 | RNA Polymerase RNA polymerase transcribes genetic information from DNA into RNA |
 | Rubisco Rubisco fixes atmospheric carbon dioxide into bioavailable sugar molecules |
 | Selenocysteine Synthase Selenium is used in place of sulfur to build proteins for special tasks |
 | Self-splicing RNA Special sequences of RNA are able to splice themselves |
 | Src Tyrosine Kinase Growth signaling proteins play an important role in the development of cancer |
 | Sulfotransferases Sulfotransferases transfer sulfuryl groups in enzymatic reactions |
 | Superoxide Dismutase Superoxide dismutase protects us from dangerously reactive forms of oxygen |
 | Tetrahydrobiopterin Biosynthesis Tetrahydrobiopterin plays an essential role in the production of aromatic amino acids, neurotransmitters and nitric oxide. |
 | Thrombin Thrombin activates the molecule that forms blood clots |
 | Thymine Dimers Ultraviolet light damages our DNA, but our cells have ways to correct the damage |
 | Tissue Transglutaminase and Celiac Disease Tissue transglutaminase staples proteins together by forming a chemical crosslink. |
 | Topoisomerases Topoisomerases untangle and reduce the tension of DNA strands in the cell |
 | Transposase Transposases shift genes around in the genome |
 | Trypsin An activated serine amino acid in trypsin cleaves protein chains |
 | Xanthine Oxidoreductase Xanthine oxidoreductase helps break down obsolete purine nucleotides |
Learning Resources (5)
 | The Structures of the Citric Acid Cycle Flyer Also known as the Krebs cycle or the tricarboxylic acid cycle, the citric acid cycle is at the center of cellular metabolism. Learn about the structures involved in this metabolic pathway. |
 | The Ribosome Flyer This flyer commemorates the 2009 Nobel Prize in Chemistry for studies of the structure and function of the ribosome. |
 | How Enzymes Work Video |
 | Ribosome: Large subunit GIF |
 | Ribosome: Small subunit GIF |
Global Health (1)
 | Diabetes Mellitus - DPP4 "This protease is responsible for cleaving various small peptides, including the incretins GLP-1 and GIP." |
Geis Digital Archive (5)
 | Lysozyme Geis illustrates the structure of lysozyme, which was first revealed by X-ray crystallography in 1965 (Blake et al., 1965). The structure of lysozyme was the first to be determined via this method. Geis carefully highlights the interaction between lysozyme and the substrate. This particular illustration appeared on the cover of Scientific American Volume 215, Issue 5 (Phillips, 1966). |
 | Lysozyme Geis illustrates the structure of lysozyme, the first enzyme structure revealed by X-ray crystallography. In this illustration, Geis carefully highlights the interaction between lysozyme and its substrate (red). |
 | Ribonuclease S Geis illustrates the structure of the ribonuclease S that highlights the dinucleotide RNA substrate in red and the four disulfide bonds in yellow. |
 | Trypsin Geis illustrates the structure of bovine trypsin, an enzyme that breaks down proteins, which was first revealed by X-ray crystallography in 1971 and further explored in 1974 (Krieger et al., 1974). This illustration was originally published in Scientific American (Stroud, 1984). Trypsin is a protease, an enzyme that catalyzes cleavage of polypeptide chains (Stroud, 1984). Geis' sketch depicts the structure with a ball-and-stick model and displays the sidechains of aspartic acid (Asp102), histidine (His57), and serine (Ser195), known as the catalytic triad. |
 | Aspartate Transcarbamoylase (ATCase) In these two paintings of ATCase, Geis portrays the structural transformation between the relaxed state (R-state) and tense state (T-state). The two catalytic trimers, illustrated with tiny specks, are seen on the top and bottom, while the three regulatory dimers, depicted with thin bands, are seen on the sides and in the back. Geis utilizes movement and shading techniques to animate the transformation. The arrows on the sides of the paintings show the directions that the enzyme is rotating in each case. |
