Enzymes Flashcards
Enzyme activity
amount of substrate turned inot product
specific activity
the activity of an enzyme per milligram of total protein
the amount of substrate converted, per mg protein in the enzyme preparation, per unit of time
turnover nummber
substrate molecules converted to product in a given unit
catalytic constant
moles product per second/moles active site
The number of molecules of substrate converted to product per unit time, when the enzyme is working at maximum efficiency.
km
substrate concentration at a velocity where vmax/2 at particular ezyme concentration
competetive inhibition
compete with substrate for active site, vmax is same, km increases
non-competetive
inhibitor binds to another site than avtive site and reduces enzyme avtivity.
Km is same, vmax decreases
un-competetive
Inhibitor binds only to the complex formed between the enzyme and the substrate.
Km and vmax decreases
Effect of enzymes
- Activation energy:
- gibbs free energy
- reaction mechanism
- equilibrium state
- time to reach equilibrium
- Decreases
- No change
- changes
- No change
- decreases
Types of enzymes
Oxidoreductases ligases lyases isomearses transferases
Acid/base catalysis
A.a side chains contribute in catalysis by acting as acid/base
Specific acid/base catalysis
Only dependent of H+ and OH, independent of concentration of acids/bases
Proteases
Enzyme that cuts proteins by hyrdolzing peptide bonds
Serine-protease
Cuts protein by hydrolyzing peptide bonds using serine in the active site of the enzyme
Inbibitor of ser protease
di-isopropyl-fluro-phosphate
irreversible inhibitor
Zygmoens/proenzyme
Inactive enzyme, can be activated by hydrolysis
enzyme induction
Process in which molecule induces expression of enzyme
specificity of serine protases
They are charachterized by distinct structure
where they can be substare specified as trypsin like, chymotrypisn, elastase like
Irreversible covalent modification
conversion of inavtive proenzyme to active enzyme by hydrolyzing peptide bonds
Reversible covalent modification
Phosphorylation/ dephosphosphorylation on the enzyme
enzyme repression
Reprseeor molecule that prevent production of enzyme.
Protein kinase
enzymes modifying enzymes by adding a phosphate group
Hill coeficcient
measuring the cooperativity between subunits
Prosthetic group
Small molecule participating in substrate binding and catalysis
Ex. FAD, bind by covalent, non-covalent
Cofactor
Small molecule participating in substrate binding and catalysis
Bind in a dissociable manner
Coenzymes
Small molecule participating in substrate binding and catalysis
Ex: Nadh, transports substrates from one place to another
Sirtuin
NAD-dependent deacetylases of histones
Play role in silencing, supression of genes near telomeres.
Catalysis Constant
Catalytic efficiency of enzymes, increasing the rate of reactions which results in a more efficient chemical reaction within a biological systems.
Line - weaver burke plo
is a graphical representation of the of enzyme kinetics where the y axis is 1/V and the x axis is 1/s. The y axis intercept is 1/vmax and the x axis is -1/Km. Slope is Km/Vmax. It demonstrates the inhibition type on an enzyme.
In active site of chymptrypsin, trypsin, elastase
chymotrypisn: Phe, Tyr, Trp
trypsin: Arg,Lys
elastase: Gly,Ala, Ser
specific constant
kcat/ km
