Enzyme kinetics Flashcards
What enzyme is required to activate chymotrypsinogen
Active trypsin is required to cleave chymotrypsinogen into its active form chymotrypsin
At which amino acid residues does chymotrypsin cleave peptide bonds
Chymotrypsin cleaves peptide chain at aromatic amino acid side residues such as tryptophan, tyrosine and phenylalanine
At which side of peptide bond does the cleavage by chymotrypsin take place
The cleavage by chymotrypsin takes place on the carboxyl side of peptide bond
What kind of enzyme is chymotrypsin
Chymotrypsin is a serine protease, with an active serine residue in its active site
What are the four functions of proteases in the body
Proteases are involved in the breakdown of digestive proteins for absorption, in cleaving other enzymes into their active forms, in degrading the ECM and in the general protein turnover in the body
What is the Vmax of an enzyme
The maximal amount of substrate that can be converted into product in a certain amount of time, depends on the Kcat and the number of enzyme molecules present
What is the Michaelis constant and symbol
Km, the substrate concentration at which the enzymes function at half their maximum velocity
What does a low Km and a high Km indicate
Low Km indicates tight binding of substrate to active site and high affinity of enzyme for substrate. High Km indicates weak binding of substrate to active site and low affinity of enzyme for substrate.
What is the steady state of an enzymatic reaction
The initial phase of an enzymatically catalysed reaction in which the reaction velocity is constant
What is the Lineweaver-Burk plot used for
Lineweaver-Burk plot is a double reciprocal graph that plots substrate concentration against initial reaction velocity. This information can be used to find the maximum velocity (Vmax) and the Michaelis constant (Km)
In what situation must the initial rate of reaction be measured
If the substrate concentration is high, the reaction velocity is shown to decrease over time so to calculate the V0 you must take the velocity at the start of reaction
How can the rate of enzyme production be measured from absorbance values
If the product or substrate in an enzymatically catalised reaction can absorb light, the decrease or increase in absorbance of a sample can be measured over time and this can be used to calculate the V0 of that reaction.
Where do competitive and non-competitive antagonists bind on enzyme
Competitive antagonists often bind in the active site of an enzyme, where non-competitive antagonists often bind further away from the active site and cause conformational changes in the enzyme that make it less accessible for the substrate.
What is the effect of a competitive antagonist on Km and Vmax
A competitive antagonist increases the Km of an enzymatic reaction, but has no effect on Vmax. Adding more substrate to solution can outcompete antagonists and so still approach Vmax. This makes the line in Lineweaver-Burk plot be steeper than without competitive inhibitor.
What is the effect of a non-competitive antagonist on Km and Vmax
A non-competitive antagonist has no effect on the Km of an enzymatic reaction, but decreases the Vmax. The inhibitor inhibits enzyme function, but does not affect the binding of substrate to enzyme in active site. This makes the line in Lineweaver-Burk plot be less steep than without non-competitive inhibitor.
