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BIOCHEM
ENZYMES
| TERMS | DEFINITION |
|---|---|
| ENZYMES | is a compound usually a protein, that acts as a naturally occurring organic catalyst that is mostly responsible for biochemical reactions in or body. |
| CATALYST | Is any substance that increases the rate of the reaction without itself being consumed. |
| FIBROUS PROTEINS | tend to have a structural role |
| SIMPLE ENZYME | composed only of protein (amino acid chain) |
| CONJUGATED ENZYME | composed of protein and non-protein parts. |
| APOENZYME | protein part of a conjugated enzyme. |
| COFACTOR | the non-protein part of a conjugated enzyme. |
| HOLOENZYME | often used to designate a biologically active combined apoenzyme-cofactor entity |
| COENZYME | a small organic molecule that serves as a cofactor in a conjugated enzyme. |
| Substrate | Reactant in an enzyme – catalyzed reaction |
| Oxidoreductase | Catalyzes an oxidation – reduction reaction. Requires a coenzyme that is oxidized or reduced as the substrate is reduced or oxidized. |
| LACTATE HYDROGENASE | an oxidoreductaste that removes hydrogen atoms from a molecule |
| Transferase | Catalyzes the transfer of a functional group from one molecule to another |
| Transaminases | Catalyzes the transfer of amino group from one molecule to another |
| Kinases | Catalyzes the transfer of phosphate group from ATP to give ADP and a phosphorylated product. |
| Hydrolase | Catalyzes the hydrolysis reaction in which the addition of a water molecule to a bond causes the bond to break Central to the process of digestion |
| Carbohydrases | effect the breaking of glycosidic bonds to oligo and polysaccharides |
| Protease | effect the breaking of peptide linkages in proteins |
| Lipases | effect the breaking of ester linkges in triaglycerols |
| Lyase | Catalyzes the addition of a group to a double bond or the removal of a group to form a double bond in a manner that does not involve hydrolysis or oxidation |
| Dehydratase | effects the removal of the components of water from a double bond |
| Hydratase | effects the addition of the components of water to a double bond |
| Isomerase | Catalyzes the isomeriz ation (rearrangements of atoms) of a substrate in a reaction converting it to a molecule isomeric with itself. One reactant and one product in reactions. |
| Ligase | Catalyzes the bonding together of two molecules into one with the participation of ATP. |
| Enzyme active site | Small part of an enzyme’s structure that is actually involved in catalysis. A three – dimensional entity formed by groups that come from different parts of the protein chains |
| Enzyme – Substrate Complex | The intermediate reaction species that is formed when a substrate binds to the active site of an enzyme. |
| LOCK-AND-KEY MODEL | Active site in the enzyme has the fixed, rigid geometrical conformation. Substrate with a complementary geometry |
| INDUCED FIT MODEL | active site is not rigid and static. There’s a constant change in shape Allows for changes in the shape or geometry of the active site of an enzyme to accommodate a substrate. Result of the enzyme’s flexibility; it adapts the incoming substrate. |
| ENZYME SPECIFICITY | Extent to which an enzyme’s activity is restricted to a specific substrate, a specific group of substrate, a specific type of chemical bond, or a specific type of chemical reaction. |
| Absolute Specificity | Catalyze only one reaction Most restrictive of all specificities is not common Catalase – enzyme with absolute specificity |
| Group Specificity | Act only on molecules that have a specific functional group, such a hydroxyl, amino or phosphate groups. Carboxylpeptidase is group specific. |
| Linkage Specificity | Act on the particular type of bond, irrespective to the rest of the molecular structure. Phosphatases hydrolyze phosphate – ester bonds in all types of phosphate esters Most general of the common species |
| Stereochemical Specificity | Act on a particular isomer |
| Enzyme Activity | Measures the rate at which an enzyme converts substrate to products in a biochemical reaction |
| Factors that affects enzyme activity | Temperature pH Substrate Concentration Enzyme Concentration |
| TEMPERATURE | Measure of kinetic energy of molecules. Higher temperatures mean molecules are moving faster and colliding more frequently |
| pH | the charge on acidic and basic amino acids located at the active site depends on ___ can result in enzyme denaturation and subsequent loss of catalytic activity. Can also affect substrate |
| Pepsin | Active in the stomach, functions best at pH 2.0 |
| Trypsin | Operates in the small intestines, function best at pH 8.0 |
| physiological pH ranges from | 7.0 – 7.5 |
| SUBSTRATE CONCENTRATION | Increased concentration of substrate will obtain the enzyme activity. |
| ENZYME CONCENTRATION | Kept in a low number because enzymes are not consumed in the reaction -the greater it is, the greater the reaction |
| Extremophile | Microorganisms that thrives in extreme environments |
| Acidophiles | Optimal growth at pH levels of 3.0 or below |
| Alkaliphiles | Optimal growth at pH levels of 9.0 or above |
| Hyperthermophile | Temperature between 80C and 122C needed to thrive |
| Halophiles | High salinity (salt), that exceeds 0.2M NaCl needed for growth |
| Cryophiles | Temperature of 15C or lower needed for growth. |
| Enzyme inhibitor | Substance that slows or stops the normal catalytic function of an enzyme by binding to it. |
| Competitive enzyme inhibitor | Molecule that sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzymes active site |
| Non-competitive Enzyme Inhibitor | Molecule that decreases enzyme activity by binding to a site on an enzyme other than the active site. |
| Irreversible Enzyme Inhibitor | Molecule that inactivates enzyme by forming a strong covalent bond to an amino acid side – chain group at the enzymes active site. Do not have structures similar to that of the enzyme’s normal substrate. |
| Regulators | Substance that bind at the regulatory sites of allosteric enzymes. |
| Positive Regulator | Increase enzyme activity The shape of the active site is changed such that it can more readily accept substrate. |
| Negative Regulator | Decrease enzyme activity Changes to the active site are such that substrate is less readily accepted. |
| FEEDBACK CONTROL | A process in which activation or inhibition of the first reaction in a reaction sequence is controlled by a product of reaction sequence. |
| Proteolytic Enzymes | Catalyzes the breaking of peptide bonds that maintain the primary structure of protein. Generated in an inactive form and converted to active form when they are needed. |
| Zymogen | Inactive precursor of a proteolytic enzyme |
| COVALENT MODIFICATION OF ENZYME | Process in which enzyme activity is altered by covalently modifying the structure of the enzyme through attachment of a chemical group or removal of a chemical group from a particular amino acid within the enzyme structure. |
| Phosphorylation | Process of addition of the phosphate group to the enzyme by protein kinases |
| Dephosphorylation | Removal of the phosphate group from the enzyme by phosphatases. |
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