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Enzymes Part I

In equilibrium the reaction is not stopped the concentrations just become constant
Keq= [product]/ [reactant]
if one arrow is larger in an eq rxn, the larger arrow denoted the more favorable direction of the reaction
if arrow on top is larger pointing to right, the [product]/ [reactant] will be greater than 1
if equilibrium arrow on bottom is larger in favor of the left side of the reaction the [product]/ [reactant] will be less than 1 because rxn favors left side
if Keq is >1, delta G will be negative; if delta G is positive, the reaction has no tendency to go forward (concentration of products higher than reactants)
if delta G is positive, the reactants are in higher concentration; Keq < 1
Enzymes are typically globular proteins; speed rxn by lowering AE
For a rxn that is zero order, the velocity doesn't depend on concentration of substrate no answer
small molecule required for enzyme activity; organic or inorganic; tight or loose cofactor
ORGANIC; LOOSELY bound enzyme, like a substrate coenzyme- Ex: NADP(H), NAD(H), ATP
organic or inorganic cofactor that is TIGHTLY bound to enzyme prosthetic group. Ex: Heme, iron- sulfur clusters, metal ions
folded polypeptide chain of a cnjugated protein apoprotein
complete, biologically active protein conjugate, consisting of folded polypeptide chains and relevant cofactors holoprotein
as temp increases, kinetic energy of molecules increase including substrate how heat affects proteins
Temperature increase affects reaction rates of proetin denaturing until max level is achieved then it drops off with further increase in temp
most animal proteins denature at 40 degrees; optimal is 37 degrees
pH can cause enzyme to perform better or worse depending on R group; if outside pH range the protein will denature; cause a configuration change
region of an enzyme that accepts substrate (and cofactors); contributes catalytic residues that directly participate in making/ breaking of bonds active site
active site is 3D and dynamic also takes up a small are and is usually a cleft or crevice
substrates are bound to active sites by non-covalent bonds
active site is specifically catered to a specific molecule no answer
If an enzyme has 5 active sites and all are filled with substrates it is saturated
Enzymes ability to reduce delta G entropy reduction; acid- base catalysis; covalent catalysis
one or more substrates bind in active site with correct orientation Entropy reduction- "S"; disorder
some enzymes can have multiple active sites true
Substrate protons important for reactivity are accepted or donated by amino acid in the active site General acid- base catalysis; structural mechanism for delta G reduction; accounts for pH dependence of enzyme activity
transient (brief) covalent bond is formed between enzyme and substrate- usually for cleavage Covalent catalysis; delta G reduction
6 classes of enzyme reactions oxidoreductase; transferase; hydrolase; lyase; isomerase; ligase/synthetase
Enzyme reactions:catalyze oxidation/reduction reactions, transfer electrons from one compound to another, thus changing the oxidation state of both substrates. Oxidoreductases:dehydrogenases (transfer H-); oxygenases (oxidizes with O2); peroxidases (i.e. catalase)
Enzyme reactions:catalyze reactions in which a functional group is transferred from one compound to another Transferases; (kinases; adds phosphate group, ATP is source of phosphate)
Enzyme reactions:cleave carbon-oxygen, carbon-nitrogen, or carbon-sulfur bonds by adding water across the bond. Hydrolases
the equation describes the relationship between rate, substrate, and Michaelis constant so the lower the Km value the higher the affinity for enzyme toward substrate (look at the graph) MM MM notes
more specific indicator of liver inflammation than AST ALT; found predominately in the liver
if AST high and ALT normal, there is likely damage to organ other than liver
cleaves C-O, C-N, or C-S bonds by adding water across bond Hydrolases
normal AST level 7-27
normal ALT level 1-21
ALT is more specific and AST may also be elevated in heart or muscles in MI or pancreatitis
too much tylenol or drinking ALT and AST levels both high
Maltose --> Glucose with Maltase enzyme hydrolase
Cleaves C-O, C-N, or C-S WITHOUT addition of water AND without oxidizing or reducing substrates Lyases; water can be a produt but not used to break hydrate the molecule
catalyze intramolecular rearrangements of functional groups that reversibly interconvert optical or geometric isomers Isomerases
catalyze formation of new chemical bonds by coupling their formation to the cleavage of a high-energy compound Ligases/Synthetases;Ligases differ from lyases in that they utilize the energy obtained from cleavage of a high-energy bond to drive the reaction usually ATP.
Enzymes that catalyze the same reaction, but differ in structure or sequence are called isoenzymes(isozymes) Ex: lactate dehydrogenase. May also have different reaction rates/tissue distributions. They usually share the same name and are differentiated by the addition of letters or numbers (i.e. LDH1, LDH2, LDH3, etc.)
direct, reversible inhibition at an enzyme’s active site by the product of the enzyme-catalyzed reaction Product inhibition; simplest form of enzyme regulation
Products can often weakly inhibit the enzymes that produced them because reactant and product are similar in structure and can compete for binding site
simplest form of enzyme regulation product inhibition
Allosteric regulators bind enzyme at a location distinct from the active site this can increase or decrease enzyme activity because it changes the conformation of the protein
when a downstream product inhibits an upstream enzyme feedback inhibition
phosphorylation reults in conformational changes that can increase or decrese an anzymes catalytic activity
protein phosphatases do what remove phosphate group from enzyme
a large inactive form of an enzyme that can be activated by proteolytic cleavage zymogen; ex: digestive enzymes are synthesized as zymogens which can be activated on demand by proteases.
Pancreatitis is causes by premature activation of digestive zymogens they end up digesting pancreatic tissue
Enzyme synthesis and deradation form of regulation that occurs over hours to days
Vmax is proportional to the amount of enzymes present amount of enzyme generated can be increased or decreased based on physiological needs; ex, insulin can induce synthesis of an enzyme
Mechanisms of Enzyme regulation (6) product inhibition; allosteric regulation; covalent modification; protein-protein regulation; zymogen cleavage; enzyme synthesis and degradation
Damaged cells can release ____when diseased isoenzymes; normally in the cell but are released into the blood
Following an acute cell damage (like heart attack) it takes how long for enzyme levels to spike? 18-36 hours; in chronic disease, like cancer, blood enzymes are elevated
most common enzymes used to diagnose MI are CK (creatine phosphokinase) and LDL (lactate dehydrogenase)
Three isozymes of Cystolic CK CK-BB; CK-MB; and CK-MM each made of two polypeptides (M or B)
CK-BB isozyme is usually seen where? In the brain
The CK-MM isozyme is usually seen where? Skeletal muscle; also in heart muscle
Which CK isozyme is more predominant in the heart? CK-MB
Baseline CK activity in the plasma is usually 95% CK-MM
Two plasma CK assays are useful in diagnosing heart attack Total Ck activity; if elevated could mean heart attack or some other muscle damaging disorder. If CK-MB is high then we know there is a heart prob
Heart attack = elevated CK-MB levels no answer
Elevated LDL1 is indicative of what? heart attack; LDL2 is normally higher but if LDL1 level surpasses it (levels are 'flipped') there is heart attack;
Total LDL elevation OTHER than the "flip" scenaario indicate what? damage or disease in a tissue other than the heart
AST indicates what liver damage; ALT also indicates but is more specific
ALP (not as frequent as ALT or AST) congestion of bile tract; GGT can also indicate this but is more specific to liver
GGT (not as frequent as AST or ALT) congestion of bile tract and or liver damage; more specific to the liver that ALP
Can dissolve a clot in an emergency; not used as maintenance med; therapuetic enzyme Streptokinase (streptase)
Reduce the size of a thrombus after a heart attack Tissue Plasminogen Activator
starves and kills acute lymphoblatic leukemia (ALL) cells Asparaginase (Elspar)
Catalyses conversion of dietary lactose to galactose and glucose Lactase (Lactaid);undigested lactose is bacterially fermented in intestines, produces gas; enzymes from Aspergillis fungi
Created by: angieryx










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