Enzymes Flashcards
(45 cards)
ACE inhibitors
- Angiotensin converting enzyme inhibitors
* ** ACE constricts blood vessels to raise BP in addition to converting angiotensin I to angiotensin II which triggers release of aldosterone from the kidney—>raising blood pressure even more - cease the ACE pathway, preventing BP elevation
Zymogens
Inactivated form of enzymes
Enzymatic Functions/Properties
Functions:
- increase rate of reaction by lowering activation energy
- stabilize transition states
- provide a favorable miroenvironment in terms of charge or pH
Properties:
- Substrate-specific
- T & pH dependent
Be Aware
I. Do not impact the thermodynamics or position of equilibrium of a rxn II. are not consumed or changed in a rxn
Enzyme Specificity
an enzyme property that explains the ability of enzymes to only catalyze rxns that involve a specific group of substrate
Enzyme Types
6 types of enzymes exist: HILLOT
- Hydrolases
- Isomerases
- Ligases
- Lyases
- Oxidoreductases
- Transferases
HILLOT
Oxidoreductases
- One type of enzyme that catalyzes oxidation-reduction rxns
- Often have cofactors like NAD & NADP that act as electron carriers
- may have dehydrogenase, reductase or oxidase as part of their name
Include both oxidants & reductants
Oxidants
electron acceptor in an oxidation-reduction rxn
Reductants
electron donors in an oxidation-reduction rxn
Transferases
One group of enzymes that catalyze transfer of a functional group from one molecule to another.
Kinases make a member of this category of enzymes!
Kinases
Transferases that move a phosphate from from ATP to another molecule.
Hydrolases
- A group of enzymes that break down a compound into 2 molecules using the addition of water.
- are named for their substrates;
I: phosphatases –>cleave phosphate
II: nucleases–>cleave nucleic acids
III: peptidases–>cleave peptides
IV: lipases–>cleave lipase
Liases (AKA Synthases)
- Category of enzymes that catalyze cleavage of one substance into two products while also catalyzing synthesis of a single substance from two reactants.
- Does not require H2O and does not catalyze oxidation-reduction rxns.
Isomerases
Group of Enzymes that catalyze rearrangement of bonds within a molecule, but can also act as transferases, oxidoreductases, and lyases.
***Catalyze rxns involving both stereoisomers and constitutional isomers.
Ligases
Enzymes that catalyze addition and synthesis rxns involving large molecules and often involve the use of ATP.
**Synthesis of smaller substances is often catalyzed by lyases.
Enzymes Grouped Based on Functional Similarity
- Lyases & Ligases (Both involved in synthesis–Lyases synthesize smaller substances whereas Ligases synthesize larger substances and involve usage of ATP)
- Isomerases & [transferases, oxidoreductases & hydrolases]
Thermodynamics
A function that relates the energy states of the reactants and products of a rxn
- -if E of R > E of P– G>0 —Rxn is Endergonic
- -if E of R < E of P– G<0 —Rxn is Exergonic
Enzyme-Substrate Complex
Compound formed as a result of a substrate’s bond with the active site of an enzyme whose formation stabilizes the transition state and reduces activation energy of a rxn
Is stabilized by
- H-bonds
- Ionic bonds
- Transient covalent bonds
Enzyme-Substrate Interaction Theories
- Lock-Key Theory
2. Induced Fit Model
Lock Key Theory
One of the theories that attempts to explain the relationship b/w an enzyme and a substrate; it describes an enzyme’s active site as a lock and the substrate as a key
***According to this theory, no alterations have to be done in the tertiary or quaternary structures of either the substrate or the enzyme
Induced-Fit Model
One of the theories that explains the relationship b/w an enzyme and a substrate.
According to this theory, the proper substrate’s binding to an enzyme’s active site induces conformational changes in the enzyme that allow it to fully wrap around the substrate; thus lowering the activation energy of the rxn.
Conformational change of the enzyme is endothermic while release of the product by the enzyme is exothermic
Cofactors/Coenzymes
- Small, non-protein compounds that bind to an enzyme’s active site to help the enzyme catalyze a rxn!
- They can function by carrying charges!
- They are stored in small quantities
if absolutely necessary for an enzyme to carry out it’s function, they’re called prosthetic groups
[coenzymes: organic compounds such as vitamins, NAD, FAD, & Coenzyme A]
[Cofactors: inorganic minerals like iron]
They are not specific to a single rxnMultiple cofactors can be used for catalyzing a single rxn**
Holoenzymes
Enzymes containing co-factors
Apoenzymes
Enzymes not containing co-factors
Water-Soluble Vitamins
Vitamins B complex & Vitamin C (Ascorbic Acid)—coenzymes that must be replenished quickly
