Flashcards in Chapter 8 Terms Deck (29):
Accelerate reactions by lowering the activation of energy.
The catalytic activity of many enzymes depends on the presence of these small molecules.
An enzyme without its cofactor is referred to as an ________.
The complete, catalytically active enzyme is called a _______.
A subdivision of cofactors; organic molecules.
Coenzymes that are tightly bound to enzymes.
Is a thermodynamic property that is a measure of useful energy, or the energy that is capable of doing work.
The rate of a reaction depends on the _______ ______ ____ _______, which is largely unrelated to the delta G of the reaction.
Free energy of activation
A transitory molecular structure that is no longer the substrate but is not yet the product. It is the least-stable and most-seldom-occupied species along the reaction pathway because it's the one with the highest free energy.
The region of an enzyme that binds the substrates and the cofactor, if any.
The process of dynamic recognition when substrate binds to enzyme.
has the units of concentration and is independent of enzyme and substrate concentrations. It's equal to the substrate concentration at which the reaction rate is half its maximal value.
Km (the Michaelis constant)
Is attained when the catalytic sites on the enzyme are saturated with substrate.
Vmax (maximal rate)
Vo=Vmax ([S] / [S] + Km)
Yields a straight line with a y-intercept of 1/Vmax and a slope of Km/Vmax. The intercept of the x-axis is -1/Km.
Lineweaver-Burk equation (double reciprocal plot)
The number of substrate molecules converted into product by an enzyme molecule in a unit time when the enzyme is fully saturated with substrate. It's equal to Kcat.
Is a measure of catalytic efficiency.
Reaction where all substrates must bind to the enzyme before any product is released.
Reaction where one or more products are released before all substrates bind the enzyme.
Double-displacement (ping-pong) reaction
These enzymes consist of multiple subunits and multiple active sites. The binding of substrate to one active site can alter the properties of other active sites in the same enzyme molecule.
Reversible inhibition where an enzyme can bind sustrate (forming an ES complex) or inhibitor (EI) but not both (ESI). It diminishes the rate of catalysis by reducing the proportion of enzyme molecules bound to a substrate. This can be overcome by the addition of more substrate.
Is distinguished by the fact that the inhibitor binds only to the enzyme-substrate complex. The binding site is created only on interaction of the enzyme and substrate. This cannot be overcome by the addition of more substrate.
The inhibitor and substrate can bind simultaneously to an enzyme molecule at different binding sites. This can bind free enzyme or the ES complex. It acts by decreasing the concentration of functional enzyme rather than by diminishing the proportion of enzyme molecules that are bound to substrate. This cannot be overcome by increasing the substrate concentration.
These react with specific side chains of amino acids.
Are molecules that are structurally similar to the substrate for an enzyme and that covalently bind to active-site residues. They are thus more specific for the enzyme's active site than are group-specific reagents.
Affinity label (reactive substrate analog)
Are modified substrates that provide the most specific means for modifying an enzyme's active site.
Mechanism-based (suicide) inhibition
Compounds resembling the transition state of a catalyzed reaction that should be very effective inhibitors of enzymes.
They are sources of insight into catalytic mechanisms; they can serve as potent and specific inhibitors of enzymes; and they can be used as immunogens to generate a wide range of novel catalysts.