Metabolic control Flashcards
Define metabolism
All chemical proceses in living organisms producing energy and growth
What is metabolomics?
The study of the range and quantity of metabolites in a system
What are the 3 purposes of metabolic control?
1 - stability within fluctuations of the environment
2 - response to change
3- control of development
By which 4 mechanisms is protein concentration controlled?
- Rate of protein synthesis and degradation
- Gene expression
- Usage of multienzyme complexes
- Compartmentalisation
By which 6 mechanisms is protein activity controlled?
1) non-covalent binding of other molecules
2) reversible covalent modifications
3) irreversible covalent changes
4) availability of substrate/cofactor
5) presence of multiple forms
6) non-covalent binding of small molecules, regulatory protein subunits and specific macromolecules
What are isoenzymes?
group of enzymes that catalyse the same reaction, with a similar sequence however subtle differences resulting in subtly different functional properties
What reaction does lactate dehydrogenase catalyse?
Pyruvate + NADH + H+ lactatate + NAD+ (important for anaerobic metabolism)
What is the structure of lactate dehydrogenase?
- 2 subunits (M- and H-) which can combine to form five different isoenzymes
- M4 predominantely found in skeletal muscle +liver
- H4 – predominantly in cardiac muscle
- MH3 , M2H2 , M3H – other tissues
Why is H4 lactate dehydrogenase an indicator of a heart attack?
When a person has a heart attack cells are ruptured and contents are released
How can different forms of lactate dehydroganse separated?
differences in charge due to small differences in sequence, causing them to behave differently in gel
What kinetic differences are there between different forms of lactate dehydrogenase?
- KM for heart form is much higher, therefore has a higher affinity for the substrate. However M form has higher Vmax
- Allows them to make metabolic requirements of tissue
What isoenzyme differences are found in skeletal muscle?
- MHC are highly conserved across types, however differences in the C-terminal domain also differences in the hinge of the light chain and the neck. Subtle differences in the ATP binding sites
- In fast fast muscle tissue there is a higher Vmax with a high affinity for ATP, opposite for slow muscle
What reaction does creatine kinase catalyse?
ATP + creatine ADP + phosphocreatine + H+
What is the structure of creatine kinase?
- 2 subunits (M and B form which are 80% similar) with the active site between them
- Homodimers (MM) found in skeletal muscle, heterodimers (MB) found in cardiac tissue
What is alcohol dehydrogenase?
- Acts on a wide variety of biological alcohols and aldehydes as well as those acquired from diet and prescription drugs
- Different forms with different Km/Vmax
