Chapter 9 ENZYMES: Regulation of Activities Flashcards

1
Q

describe the ability of animals to maintain a constant intracellular environment despite changes in their
external surroundings

A

homeostasis

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2
Q

the causative agent of plague, elaborates a protein-tyrosine phosphatase that hydrolyzes phosphoryl groups on key cytoskeletal proteins.

A

Yersinia pestis

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3
Q

the causative agent of cholera, disables sensor-response pathways in intestinal epithelial cells by ADP-ribosylating the GTP-binding proteins (G-proteins) that link cell surface receptors to adenylyl cyclase

A

Vibrio cholerae

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4
Q

The ability of enzymes to discriminate between the structurally similar coenzymes NAD+ and NADP+ also results in a form of ______

A

compartmentation

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5
Q

Decreasing the catalytic efficiency or the quantity of
the catalyst responsible for the ____ will immediately reduce metabolite flux through the
entire pathway.

A

“bottleneck” or rate-limiting reaction

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6
Q

Schoenheimer deduced that proteins exist in a state of “dynamic equilibrium” within our bodies where they are continuously synthesized and degrade

A

protein turnover

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7
Q

The synthesis of certain enzymes depends upon the presence of ____, typically substrates or structurally related compounds that stimulate the transcription of the gene that encodes them

A

inducers

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8
Q

an excess of a metabolite may curtail synthesis of its cognate enzyme via ____

A

repression

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9
Q

activity is controlled by the interaction of hormones and other extracellular signals with specific cell-surface receptors

A

transcription factors

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10
Q

Proteins are targeted to the interior of the proteasome by _____, the covalent attachment of one or more ubiquitin molecules.

A

ubiquitination

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11
Q

is catalyzed by a large family of enzymes called E3 ligases, which attach ubiquitin to the sidechain amino group of lysyl residues.

A

Ubiquitination

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12
Q

is responsible both for the regulated degradation of selected cellular proteins, for example, cyclins, and for the removal of defective or aberrant protein species.

A

ubiquitin-proteasome pathway

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13
Q

refers to the process by which the end product of a multistep biosynthetic pathway binds to and
inhibits an enzyme catalyzing one of the early steps in that
pathway

A

Feedback inhibition

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14
Q
  • bind small, physiologically important molecules to modulate enzymes
  • Usually contain multiple subunits and frequently catalyze the committed step early in a pathway
A

Allosteric Enzymes

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15
Q

the catalyst for the first reaction unique to pyrimidine biosynthesis, is a target of feedback regulation by two nucleotide triphosphates: cytidine triphosphate (CTP) and adenosine triphosphate

A

Aspartate transcarbamoylase (ATCase)

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16
Q

are those for which catalysis at the active site may be modulated by the presence of effectors at an allosteric site

A

Allosteric Enzymes

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17
Q

a phenomenologic term devoid of mechanistic implications

A

feedback regulation

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18
Q

a mechanism for regulation of enzyme activity

A

feedback inhibition

19
Q

Nerve impulses and the binding of many hormones to cell surface receptors elicit changes in the rate of enzyme-catalyzed reactions within target cells by inducing the release or synthesis of specialized allosteric effectors called ____

A

second messengers

20
Q

is the hormone molecule or nerve impulse

A

primary or first messenger

21
Q

Those effectors that increase catalytic activity are known as ___

A

Positive effectors ( Activators)

22
Q

Effectors that reduce or inhibit catalytic activity are ___

A

Negative effectors (Inhibitors)

23
Q

represents a classic example of epigenetics, the hereditary transmission of information by a means other than the sequence of nucleotides that comprise the genome

A

Histone code

24
Q

Certain proteins are synthesized as inactive precursor proteins known as ___

A

proproteins

25
Q

The proprotein forms of enzymes are termed ___

A

proenzymes or zymogens

26
Q

involves one or more highly specific proteolytic clips that may or may not be accompanied by separation of the resulting peptides

A

Selective Proteolysis

27
Q

The conformational changes that accompany selective proteolysis of ____ align the three residues of the charge-relay network, forming the catalytic site.

A

prochymotrypsin (chymotrypsinogen)

28
Q

phosphorylate proteins by catalyzing transfer of the terminal phosphoryl group of ATP to the hydroxyl groups of seryl, threonyl, or tyrosyl residues, forming O-phosphoseryl, O-phosphothreonyl, or O-phosphotyrosyl residues, respectively.

A

Protein Kinases

29
Q

The unmodified form of the protein can be regenerated by hydrolytic removal of phosphoryl groups, catalyzed by protein ____.

A

phosphatases

30
Q

permits the functional properties of the affected enzyme to be altered only for as long as it serves a specific need

A

Phosphorylation-dephosphorylation

31
Q

Types of Allosteric Effectors

A
  1. Heterotropic effectors - effector is different from substrate
  2. Homotropic effectors - the substrate itself serve as an effector
32
Q

catalyze the transfer of the acetyl group of acetyl-CoA to the ε-amino groups of lysyl residues, forming N-acetyl lysine

A

Lysine acetyltransferases

33
Q

catalyze the removal by hydrolysis of acetyl groups, regenerating the unmodified form of the protein and acetate as products

A

histone deacetylases

34
Q

use NAD+ as substrate, which yields O-acetyl ADP-ribose and nicotinamide as products in addition to the unmodified protein

A

Sirtuins

35
Q

targets multiple proteins in a pathway

A

Acetylation-deacetylation

36
Q

A mechanism of regulating enzyme activity is to sequester enzymes in compartments where access to their substrates is limited

A

Enzyme sequestration

37
Q

Inactive proenzymes are activated by ___

A

proteolysis

38
Q
  • A substance that kills bacteria or inhibits their growth
  • Exert their action on bacteria and do not affect the host organism
  • Usually inhibits specific enzymes essential to the life process of bacteria
A

Antibiotics

39
Q
  • The first antibiotic discovered by the German Gerhard Domagk
  • Inhibits bacterial growth by its competitive inhibition of PABA conversion to folate, which is essential for normal DNA synthesis
  • Humans are not affected because we do not use PABA for folate synthesis. We derive folate from our diet
A

Sulfa Drugs

40
Q
  • Discovered by Alexander Fleming while he was working with staphylococci
  • inhibits transpeptidase, an enzyme essential for bacterial cell wall synthesis
A

Penicillin

41
Q
  • One of the best broad-spectrum antibiotics

- Inhibits the enzyme DNA gyrase, which is essential for removing “kinks” formed in bacterial DNA during replication

A

Ciprofloxacin

42
Q

The final product (E) inhibits the step from A to B

A

Simple feedback inhibition

43
Q

Both final products (D,E) inhibit the first step of their own synthesis together

A

Cooperative feedback inhibition