what characteristics do all enzymes share?
85724
All enzymes are proteins that catalyze reactions and are not changed or comsumed during those reactions. They all have a temperature and a pH at which they work best. They have an active site, require a substrate, and they all lower the activation energy level required for certain reactions to occur.  \n\n\n (Ribosomes are made of two subunits - one is RNA, the other is protein - and are not enzymes.)
617250
Many vitamins function as 'co-factors' for enzymes.  \n\nTry this simple analogy.  Think of the various craftsmen that build your house as 'enzymes' (enzymes build the molecules that make your cells work).  You would need many different enzymes to build your house: general contractor, roofer, electrician, plumber, carpenter, painter, etc.  \n\nEach craftsman ('enzyme') will need one or more 'co-factors' to do his/her job.  The painter will need a few paint brushes and a ladder for co-factors.  The carpenter will need a saw and a hammer, etc. \n\nThe painter, carpenter, plumber, etc. only need a 'small number' of co-factors to do their 'enzyme' work - but without their 'co-factors' they can't do much work at all!\n\nHope this is helpful.  Best wishes.
582504
Another important thing to note about an enzyme is that it isn't used up in the reaction, so it can be recycled over and over. An enzyme is a protein that helps in a chemical reaction to speed it up. Enzymes are very specific in the reactions that they will interact with. An enzyme will only catalyze its own reaction.
723844
All enzymes are produced in response to the presence of substrate.
916321
Enzymes are proteins.  High temperatures cause proteins to denature and, therefore, cause enzymes not to work.  Every enzyme has an optimal pH, at which point the reaction happens most quickly.  Also, the reaction happens most efficiently when the concentration of enzyme is in balance with the concentration of the substrate.  When a competitive inhibitor is present, the substrate sites on the enzymes become blocked and the reaction cannot take place.
658088
Enzymes with different structures that catalyze the same reactions are called isoenzymes.  There can be many isoenzymes for one enzyme.  For example, lactate dehydrogenase has 5 different fractions.  They are LD1, LD2, LD3, LD4, and LD5.  They are named for the migration patterns in electrophoresis (the fraction that migrates the furthest, or goes fastest, is 1, and the slowest is 5.  Each LD fraction has a different combination of 2 subunits, H and M.  LD1 is HHHH, LD3 is HMMM, and LD5 is MMMM.
767494
enzymes are protein.a change in ph results in a change in ions concentration.this changes the shape of the active site of enzyme.so the enzyme stops functioning
151784
Restriction Enzymes: \n\n \n\nThese are enzymes that cleave the strands of DNA at specific sites, according to the nucleotide sequence. They are counterparts of proteolytic enzymes such as trypsin, chymotrypsin in the world of nucleic acids. They are highly specific, and the sites they recognize may be very rare. Restriction enzymes are found in nature, primarily produced by bacteria as part of a defense system. \n\nThere are several types of restriction enzymes. We will focus on Type II, which is the type most widely used experimentally. \n\nNuclease: an enzyme that cleaves a nucleic acid\n\nRestriction Endonuclease: an enzyme that cleaves within a segment of nucleic acid, when it recognizes a specific sequences of bases. (Restriction enzyme)\n\nTypically, they are dimeric, and cleave at symmetrical sequences of DNA.\n\nExamples EcoR I and BamH I\n\n(See Chime link)\n\nHow do Restriction Enzymes recognize particular sequences of DNA?\n\nDo they open up the strands, in order to see the bases?\n\nNo, they bind along the major or minor grooves, and interact with the edges of the bases, for sequences specificity, \n\nand also with the sugars and the phosphates, for non-specific binding. This involves, H-bonding, hydrophobic contacts, and electrostatic interactions (ion pairs).
1045054
Enzymes are substance specific.  That means that enzymes only act on their target substances, so an enzyme that works on proteins would not perform a chemical reaction when it is placed in lipids.\n\nAn enzyme is a molecule that catalyzes, or speeds up, a chemical reaction.  It does this by lowering the activation energy necessary to begin the reaction.\n\nEnzymes are essential to sustain life because most chemical reactions in biological cells would occur too slowly, or would lead to different products without enzymes.  The deletion of an enzyme would cause severe disease.\n\nEnzyme activity is affected by many external factors, such as temperature, pH, and amount of substrate.
56873
The first answer is right on. But remember this as well: enzymes also have some ability to "buffer" the solution they are in as well! Because proteins (enzymes) have many chemical groups that can bind multiple hydrogen groups, its able to buffer to some extent. Generally speaking though, you'd need  a LOT of enzyme to really buffer a solution...so usually we don't worry about it!!
498975
An enzyme is a protein that catalyzes, or speeds up, a chemical reaction. The word comes from the Greek ένζυμο, énsymo, which comes from én ("at" or "in") and simo ("leaven" or "yeast"). Certain RNAs also have catalytic activity, but to differentiate them from protein enzymes, they are referred to as RNA enzymes or ribozymes.\n\nEnzymes are essential to sustain life because most chemical reactions in biological cells would occur too slowly, or would lead to different products without enzymes. A malfunction (mutation, overproduction, underproduction or deletion) of a single critical enzyme can lead to a severe disease. For example, the most common type of phenylketonuria is caused by a single amino acid mutation in the enzyme phenylalanine hydroxylase, which catalyzes the first step in the degradation of phenylalanine. The resulting build-up of phenylalanine and related products can lead to mental retardation if the disease is untreated.\n\nLike all catalysts, enzymes work by providing an alternate pathway of lower activation energy of a reaction, thus allowing the reaction to proceed much faster. Enzymes may speed up reactions by a factor of many millions. An enzyme, like any catalyst, remains unaltered by the completed reaction and can therefore continue to function. Because enzymes do not affect the relative energy between the products and reagents, they do not affect equilibrium of a reaction. However, the advantage of enzymes compared to most other catalysts is their sterio-, regio- and chemoselectivity and specificity.\n\nEnzyme activity can be affected by other molecules. Inhibitors are naturally occurring or synthetic molecules that decrease or abolish enzyme activity; activators are molecules that increase activity. Some irreversible inhibitors bind enzymes very tightly, effectively inactivating them. Many drugs and poisons act by inhibiting enzymes. Aspirin inhibits the COX-1 and COX-2 enzymes that produce the inflammation messenger prostaglandin, thus suppressing pain and inflammation. The poison cyanide inhibits cytochrome c oxidase, which effectively blocks cellular respiration.\n\nWhile all enzymes have a biological role, some enzymes are used commercially for other purposes. Many household cleaners use enzymes to speed up chemical reactions ( e.g., breaking down protein or starch stains in clothes).\n\nMore than 5,000 enzymes are known. Typically the suffix -ase is added to the name of the substrate (e.g., lactase is the enzyme that catalyzes the cleavage of lactose) or the type of reaction (e.g., DNA polymerase catalyzes the formation of DNA polymers). However, this is not always the case, especially when enzymes modify multiple substrates. For this reason Enzyme Commission or EC numbers are used to classify enzymes based on the reactions they catalyze. Even this is not a perfect solution, as enzymes from different species or even very similar enzymes in the same species may have identical EC numbers.\nIn enzymes, as with other proteins, function is determined by structure. An enzyme can be:\n\n    * A monomeric protein, i.e., containing only one polypeptide chain, typically one hundred or more amino acids; or\n    * an oligomeric protein consisting of several polypeptide chains, different or identical, that act together as a unit.\n\nAs with any protein, each monomer is actually produced as a long, linear chain of amino acids, which folds in a particular fashion to produce a three-dimensional product. Individual monomers may then combine via non-covalent interactions to form a multimeric protein. Many enzymes can be unfolded or inactivated by heating, which destroys the three-dimensional structure of the protein.\n\nhttp://en.wikipedia.org/wiki/Enzyme#3D_Structure
1102769
Active and passive. Effectors change the function of the allosteric enzymes, and can make enzymes either active (allosteric activation) or passive (allosteric inhibition).
1024663
saliva, enzymes, bacteria
317821
(m)\n\nmetabolic pathway analysis, it should be considered that many enzymes operate with low specificity (e.g. nucleoside diphosphokinase, uridine kinase, transketolase, aldolase), so that various substrates and products can be converted. Here, we analyze the effect of enzymes with low substrate specificity on the elementary flux modes (pathways). We also study the benefits of two different approaches to describing multifunctional enzymes. The usual description is in terms of (overall) enzymatic reactions. At a more detailed level, the reaction steps (half-reactions, hemi-reactions) of the formation and conversion of enzyme-substrate complexes are considered. Multifunctional enzymes operate according to various mechanisms. This is illustrated here by the reaction schemes for the different enzyme mechanisms of bifunctional enzymes. For enzymes with two or more functions, it is important to consider only linearly independent functions, because otherwise cyclic elementary modes would occur which do not perform any net transformation. However, the choice of linearly independent functions is not a priori unique. We give a method for making this choice unique by considering the extreme pathways of the hemi-reactions system. A formal application of the algorithm for computing elementary flux modes (pathways) yields the result that the number of such modes sometimes depend on the level of description if some reactions are reversible and the products of the multifunctional enzymes are external metabolites or some multifunctional enzymes partly share the same metabolites. However, this problem can be solved by appropriate interpretation of the definition of elementary modes and the correct choice of independent functions of multifunctional enzymes. The analysis is illustrated by a biochemical example taken from nucleotide metabolism, comparing the two ways of description for nucleoside diphosphokinase and adenylate kinase, and by several smaller examples.
131053
enzyme, biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.\n \n Louis Pasteur recognized in 1860 that enzymes were essential to fermentation but assumed that their catalytic action was inextricably linked with the structure and life of the yeast cell. Not until 1897 was it shown by German chemist Edward Büchner that cell-free extracts of yeast could ferment sugars to alcohol and carbon dioxide; Büchner denoted his preparation zymase. This important achievement was the first indication that enzymes could function independently of the cell.\n \n The first enzyme molecule to be isolated in pure crystalline form was urease, prepared from the jack bean in 1926 by American biochemist J. B. Sumner, who suggested, contrary to prevailing opinion, that the molecule was a protein. In the period from 1930 to 1936, pepsin, chymotrypsin, and trypsin were successfully crystallized; it was confirmed that the crystals were protein, and the protein nature of enzymes was thereby firmly established.\n \n Enzymatic Action\n \n Like all catalysts, enzymes accelerate the rates of reactions while experiencing no permanent chemical modification as a result of their participation. Enzymes can accelerate, often by several orders of magnitude, reactions that under the mild conditions of cellular concentrations, temperature, pH, and pressure would proceed imperceptibly (or not at all) in the absence of the enzyme. The efficiency of an enzyme's activity is often measured by the turnover rate, which measures the number of molecules of compound upon which the enzyme works per molecule of enzyme per second. Carbonic anhydrase, which removes carbon dioxide from the blood by binding it to water, has a turnover rate of 106. That means that one molecule of the enzyme can cause a million molecules of carbon dioxide to react in one second.\n \n Most enzymatic reactions occur within a relatively narrow temperature range (usually from about 30°C to 40°C), a feature that reflects their complexity as biological molecules. Each enzyme has an optimal range of pH for activity; for example, pepsin in the stomach has maximal reactivity under the extremely acid conditions of pH 1–3. Effective catalysis also depends crucially upon maintenance of the molecule's elaborate three-dimensional structure. Loss of structural integrity, which may result from such factors as changes in pH or high temperatures, almost always leads to a loss of enzymatic activity. An enzyme that has been so altered is said to be denatured \n \n Consonant with their role as biological catalysts, enzymes show considerable selectivity for the molecules upon which they act (called substrates). Most enzymes will react with only a small group of closely related chemical compounds; many demonstrate absolute specificity, having only one substrate molecule which is appropriate for reaction.\n \n Numerous enzymes require for efficient catalytic function the presence of additional atoms of small nonprotein molecules. These include coenzyme molecules, many of which only transiently associate with the enzyme. Nonprotein components tightly bound to the protein are called prosthetic groups. The region on the enzyme molecule in close proximity to where the catalytic event takes place is known as the active site. Prosthetic groups necessary for catalysis are usually located there, and it is the place where the substrate (and coenzymes, if any) bind just before reaction takes place.\n \n The side-chain groups of amino acid residues making up the enzyme molecule at or near the active site participate in the catalytic event. For example, in the enzyme trysin, its complex tertiary structure brings together a histidine residue from one section of the molecule with glycine and serine residues from another. The side chains of the residues i
102190
Some enzymes will be destroyed. But most will still work. Remember every enzyme has has an optimum envornment that it works at i.e. temperature and pH. So when it gets to 112 a lot of enzymes are not working at their best to sustain life.
749460
They are. they have the 5 characteristics of life\nMade of cells\nRequire nutrition\nexcretion (CO2)\nResponse (to light)\nReproduction.