Chapter 10. Regulatory Strategies

Question 1

a mode of enzyme regulation in which the end product of a biosynthetic pathway inhibits the enzyme that catalyzes the first step in that pathway.

Answer 1

Feedback (end-product) inhibiton

Question 2

a model explaining the kinetics of allosteric enzymes in which the transition of all of the active sites between the T state and the R state occur simultaneously.

Answer 2

Concerted mechanism

Question 3

A site distinct from the active site at which regulatory molecules bind and alter the enzyme activity.

Answer 3

allosteric (regulatory) site

Question 4

idealized base sequence which represents common features of a promoter site.

Answer 4

Consensus sequence

Question 5

property of many allosteric enzymes in which binding of substrate to one active sites favors the transition of all active sites from the T state to the R state, leading to an increase in enzyme activity.

Answer 5

Cooperativity

Question 6

the effects of substrate molecules on allosteric enzymes.

Answer 6

Homotropic effect

Question 7

a model to explain allosteric enzymes in which the binding of one substrate influences the substrate affinity of neighboring active sites without necessarily inducing a transition encompassing the entire enzyme.

Answer 7

Sequential model

Question 8

the attachment to and removal of chemical groups from an enzyme and the consequent change in the catalytic properties of that enzyme. Catalytic properties of many enzymes are altered by the covalent attachment and removal of phosphoryl groups, while a lesser number of others undergo reversible attachment of AMP units from ATP.

Answer 8

Covalent modification

Question 9

Blood-clotting cascade of enzyme activities that is initiated by the activation of factor VII and the release of the lipoprotein tissue factor, both of which are triggered by tissue trauma.

Answer 9

Extrinsic pathway

Question 10

The process of blood clot formation and dissolution.

Answer 10

hemostasis

Question 11

A sequence of reactions in which, at each step, a product stimulates an ensuing reaction, generating an amplification of a relatively small stimulus or signal.

Answer 11

Enzymatic cascade

Question 12

enzymes in an organism that catalyze the same reaction but differ in structure; these differences may range from one to several amino acid residues.

Answer 12

Isozyme (isoenzyme)

Question 13

the effects of non-substrate molecules on allosteric enzymes

Answer 13

Heterotropic effect

Question 14

enzymes that hydrolyze phosphorylated serine and threonine residues in other proteins. Protein phosphatase 1 reverses the regulatory effects of kinases on glycogen metabolism.

Answer 14

Protein phosphatase

Question 15

an amino acid sequence that resembles the actual substrate for an enzyme except that a crucial amino acid has been changed, converting the sequence into an inhibitor. The regulated binding of pseudosubstrates is sometimes used to control enzyme activity.

Answer 15

Pseudosubstrate sequence

Question 16

a protein kinase that consists of two catalytic subunits and two regulatory subunits, which inhibit the catalytic subunits. Upon binding of cAMP, the regulatory subunits dissociate from the catalytic subunits, which then become active.

Answer 16

Protein kinase A (PKA)

Question 17

The-blood clotting cascade of enzyme activities that is initiated by the activation of factor XII through contact of activating proteins (kininogen and kallikrein) with abnormal cell surfaces produced by injury; at least six proteins are activated in the pathway to thrombin formation and the continuing sequence that leads to a blood clot.

Answer 17

Intrinsic pathway

Question 18

a catalytically inactive precursor of an enzyme.

Answer 18

Zymogen (proenzyme)

Question 19

a class of enzymes that transfer a phosphoryl group from ATP to proteins; protein kinases are frequently found in regulatory pathways.

Answer 19

Protein kinase