Biological molecules (proteins) that act as catalysts and help complex reactions.
are specific to their substrates and each enzyme has its own optimum pH
Material upon which an enzyme acts.
important in normal metabolism for control of pathways.
(Raises Km only) Same size and shape with the substrate
(Lowers Vmax only) inhibitor doesn't mind whether there is a substrate or not. but when the inhibitor binds, it switches off catalysis.
(Lowers Vmax and Km) the inhibitor can ONLY be on the surface of the enzyme if the substrate is there.
acts by reacting with the enzyme protein, usually at the active site(substrate site), to permanently block activity.
Vmax is the maximum rate of an enzyme catalysed reaction i.e. when the enzyme is saturated by the substrate.
Km is measure of how easily the enzyme can be saturated by the substrate.
Km and Vmax are constant for a given temperature and pH and are used to characterise enzymes. They can be used to identify types of inhibitors i.e. competitive, non-competitive and uncompetitive.
Enzyme in human digestion
In the case of metal ion cofactors
Stabilise the structure, not directly involved in the chemistry
Ca++ with some proteinases
part of substrate
Mg++-ATP with some kinases
part of active site
Zn++ in alcohol dehydrogenase
they do come on and off like other substrates (NAD+)
a cofactor that forms a permanent part of the enzyme's active site.
Doesn't come on and off in a catalytic cycle (FAD,PLP)
NAD+ is both a coenzyme and a substrate
Why use coenzyme in one case and not in the other case?
Metabolic point: NAD is one of a range of cofactor substances that is present in small concentration
They turn over and over again to process a large amount of substances
Pathway is to process large amount with tiny amount of coenzyme