Bch 451 Exam 2

Front 1

acid-base catalysis

Back 1

Transfer of proton from substrate to substrate, or substrate to enzyme.

Front 2

covalent catalysis

Back 2

Does not involve proton. Substrate or Enzyme attacks Substrate (nucleophilic).

Front 3

intermediate formation

Back 3

Baby-step process; breaking down the entire energy hill into smaller hills with lower activation energy.

Front 4

Proximity effect

Back 4

Limit the rotation and translation (degrees of freedom). Effectively more locally concentrated.

Front 5

transition state stabilization

Back 5

Increased interaction of transition state with the enzyme.

Front 6

intermediates

Back 6

quasi-stable step between substrate and product; sometimes able to be isolated.

Front 7

transition state analog

Back 7

a stable molecule that resembles a proposed transition state; normally an effective inhibitor.

Front 8

transition state

Back 8

the fleeting and unstable stage of a substrate, characterized by distorted bond lengths and angles, as it is converted to product; not able to be isolated.

Front 9

Other Teachers Have Lied in Lecture.

Back 9

Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases.

Front 10

active site

Back 10

the portion of an enzyme that contains the substrate-binding site and the amino-acid residues involved in catalyzing the conversion of S to P. Usually found in clefts between domains or subunits of proteins, or in indentations on the protein surface.

Front 11

allosteric site

Back 11

(regulatory site) a ligand-binding site in a regulatory enzyme distinct from the active site. Allosteric modulators alter enzyme activity by binding to the regulatory site.

Front 12

catalytic site

Back 12

the location on an enzyme where the substrate(s) react with each other and/or portions of the enzyme.

Front 13

daltons

Back 13

A unit of mass = 1 amu.

Front 14

isozymes

Back 14

different proteins from a single biological species that catalyze the same reaction.

Front 15

Ki

Back 15

inhibition constant. Characterizes the equilibrium between free enzyme (E) plus inhibitor (I) and the EI complex. Dissociation constant.

Front 16

Km

Back 16

Michaelis constant. The [S] that results in Vo equal to 1/2 Vmax for a given reaction.

Front 17

specificity constant

Back 17

Kcat/Km. The second-order rate constant for conversion of ES -> E + P at low [S]. The ratio of Kcat to Km, when used to compare several substrates, is called specificity constant

Front 18

substrate binding site

Back 18

the location on the enzyme where substrate(s) bind to the enzyme. Occurs thru variety of forces and determines the specificity of the enzyme for different substrates.

Front 19

Vmax

Back 19

initial velocity of rxn when enzyme is saturated with substrate. k2 [E2] = Vmax (E2 = Etotal)

Front 20

zymogens

Back 20

a catalytically inactive enzyme precursor that must be modified by limited proteolysis to become enzymatically active.

Front 21

List the steps outlined in Knopps' Knotes that determine Km and Vmax:

Back 21

Determine [S] and Evelocity. Take reciprocals. Graph them (Y = velocity, X = concentration). Fit a line to pts. Take reciprocals of intersects. Y = Vmax, X = Km.