Enzymes Flashcards
What is a ribozyme?
A type of RNA that acts as a biological catalyst
What is a glycogen storage disease?
An enzyme deficiency that results in failure to break down glycogen
What are the 3 reactions (Enzymes) of glycogenolysis?
Glycogen —> Glucose-1-phosphate
(Glycogen phosphorylase)
G-1-P —> Glucose-6-phosphate (Phosphoglucomutase)
G-6-P —> Glucose
(Glucose-6-phosphatase)
Which enzyme is affected by Von Gierke’s disease (Glycogen storage disease type I)
Glucose-6-phosphatase
What are the symptoms of Von Gierke’s disease?
Hypoglycaemia
Hepatomegaly (Liver swelling)
Mouth ulcers
Skin ulcers
Infection
Bowel inflammation and irritability
What is a cofactor?
A metal ion that associates with an enzyme to allow it to perform its function
What is a coenzyme?
An organic molecule that associates with an enzyme that helps it to perform its function
What name is given to an enzyme when incorporated with a metal cofactor?
A metalloprotein
What name is given to an enzyme without a cofactor?
An apoenzyme
What name is given to an enzyme with a cofactor?
A haloenzyme
What name is given to a tightly bound coenzyme?
A prosthetic group
What are isozymes?
Isoforms of an enzyme; they catalyse the same reaction but have different properties and structures
What are the 2 subunits of lactate dehydrogenase?
H (heart) and M (muscle)
What are the functions of H and M lactate dehydrogenase?
H promotes aerobic metabolism
M promotes anaerobic metabolism
What reaction does HLDH promote?
Lactate —> Pyruvate
What are the 5 isoforms of LDH?
LDH-1 - 4H subunits
LDH-2 - 3H1M subunits
LDH-3 - 2H2M subunits
LDH-4 - 1H3M subunits
LDH-5 - 4M subunits
Which gene codes for the heart subunit?
LDHB
What gene codes for the muscle subunit?
LDHA
How is the LDHA gene turned on?
Disease causes hypoxia
Hypoxia stimulates the release of hypoxia sensitive transcription factors
These transcription factors bind to the hypoxia response element in the promoter region of LDHA
What type of enzyme carries out phosphorylation reactions?
Protein kinases
What is the function of phosphorylation?
It can convert an enzyme to either an active or inactive form to regulate the reaction
What type of enzyme removes a phosphate group?
Phosphatases
What is a zymogen?
An inactive precursor of an enzyme that is irreversibly transformed into an active enzyme
What is the zymogen of trypsin?
Trypsinogen
What is the zymogen of chymotrypsin?
Chymotryspinogen
What converts trypsinogen to trypsin?
Enteropetidase
What is Vmax?
The maximum rate at which an enzyme can convert a substrate
What is 1/2 Vmax?
Half of the maximum rate at which an enzyme can convert a substrate
What is Km
The Michaelis constant:
The substrate concentration at which 1/2 Vmax is reached
What are the 3 reactions of an enzyme controlled reaction?
E + S —–> ES (K1)
ES —-> E + S (K-1)
ES —-> E + P (K2)
What is the formula for Km using K1, K2 and K-1?
Km = (K-1 + K2) / K1
What is the Michaelis-Menten equation of V (velocity of a reaction)?
V = Vmax [S] / Km + [S]
