Enzyme Kinetics

What do enzymes do to the transition state

Lower its energy

What are co-factors

non-protein molecules needed for full catalytic activity. They can be permanent prosthetic groups or transient co-substrates.

Types of enzyme names

How does the concentration of enzyme and product change over time in a reaction

The product line gradient maxes out as the ES line plateaus.

How does the overall reaction look over a longer time

Binding efficiency can be determined.

What 4 assumptions do we make about catalytic reactions for kinetics

What happens if you increase concentration of the substrate while enzyme conc does not change

Increased concentration of substrate allows more complexes to form. Once V_max is reached, the enzyme is fully saturated and no further increases will occur.

How can K_m be determined

defining K_M and K_cat (last few slides of lecture 16)

K_M is the concentration of substrate which permits the enzyme to achieve half V_max. Essentially it measures the affinity of the enzyme for the substrate i.e. how likely they are to bind to each other.

The catalytic constant (k_cat) is another name for k₂ and measures how fast the ES progresses to E + P i.e. how fast the enzyme reaction process occurs.

What is a way to represent enzyme catalytic ability

This value is substrate specific

What are diffusion limits

Essentially a maximum affinity for enzymes relying on diffusion

What factors can inhibitors affect

What are uncompetitive inhibitors

Only binds to the ES complex

Irreversible inhibition

Functions similarly to non-competitive inhibition in that it only affects V_Max. Eventually the inhibitor will be entirely used up.

Measures of potency of an inhibitor

What is interfacial catalysis

Enzyme needs to be on the membrane to function. Scooping happens over hopping when the membrane affinity is low compared to that of the substrate

What is cooperativity

One molecule favours the binding of an additional molecule. In the context of enzymes induced fit can be induced by another substrate binding at a second binding site. This increases the enzyme’s affinity

What is allostery

An activator can bind to an allosteric site (subunit), increasing affinity of the enzyme by inducing a change in the active site shape.

This goes the other way with inhibitors

Activators/inhibitors are modulators.

What is homotropic allostery

Cooperativity as seen in Hb - the modulator is the substrate.

Heterotropic modulators

Modulators that are not substrates.

What is R-state and T-state

Relaxed state - heightened affinity, cooperativity

Tense state - reduced affinity, inhibition

What ways can enzymatic reactions proceed if there are 2 substrates