Enzyme Properties and Kinetics - Exam Questions Flashcards
The active site of an enzyme…
…is complementary to the transition state
Give an example of an oxidoreductase.
Lactate dehydrogenase
What do lyases catalyse?
The cleavage of C-C, C-O or C-N bonds
What is the fastest rate of enzyme-catalysed reactions in the human body?
50oC
What is the optimal pH of enzyme catalysed reaction in the human body?
Varies for each enzyme
Cu2+ is a co factor for:
a. trypsin
b. chymotrypsin
c. urease
d. glutathione peroxidase
e. cytochrome oxidase
e. Cu2+ is a cofactor for cytochrome oxidase
What is Fe2+/Fe3+ a co factor for?
Cytochrome oxidase
K+ is a co-factor for.?
Pyruvate kinase
Mg2+ is a cofactor for?
pyruvate kinase
Ni2+ is a cofactor for..?
urease
Se is a cofactor for..?
Glutathione peroxidase
Zn2+ is a cofactor for..?
Carbonic anhydrase
What are isoenzymes?
Different proteins that catalyse the same reaction.
What is the Michaelis-Menten equation?
V0=Vmax[S]/(Km+[S])
Km is…
Km = [S] when V0=0.5Vmax
Km = k2+k-1/k1. Km represents the affinity of enzyme for its substrate…
…when k2 becomes negligible
What is Kcat?
The number of product molecules produced by one active site of an enzyme per unit time
The catalytic efficient of enzymes is best compares by..?
Kcat/Km
The Lineweaver - Burker plo…
…uses the inverse of the Michaelis-Menten equation
Where is 1/Vmax found on the Lineweaver-Burke plot?
At the interception of the Y-axis
When will the enzymes ALT, troponin-t and CK be significatly raise in the blood.
Because they have escaped damaged tissues.
Where is lactate dehydrogenase found?
Exists as a tetramer of heart or muscle subunits
What do competitive inhibitors do to the Km?
Increases the Km
Non competitive inhibitors…?
Lower the Vmax
How can acetylcholinesterase by inhibited?
Can be inhibited reversibly by neostigmine
Enzyme kinetics show a sigmoid curve when regulated…
a. by phosphorylation
b. be induction or repression of enzyme synthsis
c. allosterically
d. by adenylation
e. by ADP-ribosylation
c. Enzymes kinetics show a sigmoidal curve when regulated allosterically.
Phosphorylation of enzymes:
Often adds a phosphate group to a serine residue
ADP-ribosylation function..
..requires NAD as a reactant
What is allosteric control of an enzyme typically effected by?
End-product inhibition
