E1 Flashcards
The most critical function of an enzyme
catalyze reactions.
Common features of enzymes
- Catalyze – reaction still could occur.
- Enzyme not permanently altered by rxn.
- Can catalyze both forward and reverse rxn.
- Highly specific for substrate.
Influence of temperature and PH on enzyme
Denatures, folding, stability
Composition of complex enzyme
Quarternary structure ** more on this?
Oxidoreductase
Catalyze transfer of electrons from one molecule (reductant) to another (oxidant). Oft uses NAD+/NADH.
Transferase
Transfer a group from one molecule to another.
Hydrolase
Add H20
Isomerase
Rearange molecules to differing isomers
Ligase
Remove H20, bring two molecules to one.
Active site(s) of enzymes
fisher, other
Absolute (only 1 rxn) and relative (more than 1) specificities of enzymes
*
Definition of enzyme activity
1 unit (U) is the amount if enzyme that catalyses the reaction of 1 nmol of substrate per minute under standard conditions.
Km
amount of substrate needed for the enzyme to obtain half of its maximum rate of reaction, Max velocity respectively
Reversible and irreversible inhibition of enzyme
competitive, noncomp, uncomp, suicide, group-specific reagents (react with specific AA R-groups), substrate analogs (covalently modify site, like substrate)
Regulation of enzyme activity
(allosteric (2nd site from active site), reversible covalent (phosphate group most common), isoenzymes, proteolytic (cleavage, can activate, can destroy).
Metabolic channeling
Occurs when the product of one reaction is transferred directly to the next active site without entering the bulk solvent. Can greatly increase rate of a reactions
Channeling is possible in
Channeling is possible in multienzyme complexes and multifunctional enzymes
Glycolysis starts from glucose and ends at
lactate
Glucose can be used to generate
ATP, glycogen, ribose, lipid molecules, and NADPH*
Glucose can be trapped in a cell in the form of
Glc-6-P
The rate limiting enzyme of glycolysis is
PFK-1
Enzymes for glycolysis yield
PGK and pyruvate kinase catalyze the yield of ATP in glycolysis
Pyruvate can be transformed to
lactate in order to regenerate NAD+
Glc-6-P
Hexokinase can be inhibited by Glc-6-P