Biochemistry ~ Enzymes Lehninger Key Terms

Front 1

THe ability of an enzyme or receptor to discriminate among competing substrates or ligands

Back 1

Specificity

Front 2

The proportionality constant that relates the velocity of a chemical reaction to the concentration(s) of the reactants

Back 2

Rate Constant

Front 3

A constant, characterstic for each chemical reaction; relates the specific concentrations of all reactants and products at equilibrium at a given temperature and pressure

Back 3

Equilibrium constant {K[eq]}

Front 4

Any chemical species in a rxn pathway that has a finite chemical lifetime

Back 4

Rxn intermediate

Front 5

The energy derived from noncovalent interactions between enzyme and substrate or receptor and ligand

Back 5

binding energy {delta G [B]}

Front 6

1. Generally the step in an enzymatic rxn with the greatest activation energy or the transition state of the highest free energy

2. The slowest step in a metabolic pathway

Back 6

rate limiting step

Front 7

The specific compound acted upon by an enzyme

Back 7

Substrate

Front 8

The normal, stable form of an atom or molecule; as distinct from the excited state

Back 8

Ground State

Front 9

The free-energy change for a reaction occuring under a set of standard conditions: Temp 298 k; pressure 1 atm or 101.3 kPa; and all solutes at 1 M concentration

Back 9

Standard free- energy change

Front 10

The amount of energy (in J) required to convert all the molecules in 1 mole of a reacting substance from the ground state to the transition state

Back 10

Activation energy

Front 11

An activated form of a molecule in which the molecule has undergone a partial chemical rxn; the highest point on the reaction coordinate

Back 11

Transition state

Front 12

A Metal ion or an organic compound (other than an A.A) that is convalently bound to a protein and is essential to it's activity

Back 12

Prosthetic group

Front 13

A catalytically active enzyme including all necessary subunits, prothetic groups, and cofactors

Back 13

Holoenzyme

Front 14

The protein portion of an enzyme, exclusive of any organic or inorganic cofactors or prosthetic groups that might be required for catalytic activity

Back 14

Apoenzyme

Front 15

The protein portion of a protein, exclusive of any organic or inorganic cofactors or prosthetic groups that might be required for activity

Back 15

Apoprotein

Front 16

The region of an enzyme surface that binds the substrate molecule and catalytically transforms it; also know as the catalytic site

Back 16

Active site

Front 17

An organic cofactor required for the action of certain enzymes; often contains a vitamin as a component

Back 17

Coenzyme

Front 18

An inorganic ion or a coenzyme required for enzyme activity

Back 18

Cofactor

Front 19

A biomolecule, either protein or RNA, that catalyzes a specific chemical rxn. It does not affect the equilibrium of the catalyzed reaction; it enhances the rate of a rxn by providing a reaction path with a lower activation energy

Back 19

Enzyme

Front 20

Enzymes that transfer the terminal phosphoryl group of ATP or another nucleoside triphosphate to a Ser, Thr, Tyr, Asp, or His side chain in a target protein. Thereby regulating the activity or other properties of that protein

Back 20

Protein Kinases

Front 21

An enzyme having a regulatory function through its capacity to undergo a change in catalytic activity by allosteric mechanisms or by covalent modification

Back 21

regulatory enzymes

Front 22

A regulatory enzyme with catalytic activity modulated by the non-covalent binding of a specific metabolite at a site other than the active site

Back 22

allosteric enzymes

Front 23

Inhibition of an allostericenzymes at the beginning of a metabolic sequence by the end product of the sequence; AKA end product inhibition

Back 23

Feedback inhibition

Front 24

An inactive precursor of an enzyme; Ex. pepsinogen, the precursor of pepsin

Back 24

Zymogen