mobilization of amino acids

Question 1

what a-keto acids in metabolism do you need to know the structures of?

Answer 1

pyruvate, oxaloacetate, a-ketoglutaratew

Question 2

what are the central pathways in metabolism?

Answer 2

glycolysis, gluconeogenesis, Krebs Citric Acid Cycle, Oxidative Phosporylation

Question 3

what is essential for efficient metabolism?

Answer 3

a-keto-acids (too little, not good; too much, not good)

Question 4

what do transaminases do?

Answer 4

catalyze two half reactions
sum: AA1+a-Keto2<=>AA2+a-Keto1

Question 5

1st half reaction of enzyme-bound reactions

Answer 5

aldimine forms
converts to ketimine
hydrolyzes to ketoacid

Question 6

2nd half reaction of enzyme-bound reactions

Answer 6

is reverse of 1st half reaction, using R2-KA to make R2-AA

Question 7

know the structures of aldimine and ketimine for what?

Answer 7

enzyme bound reactions

Question 8

what is true about all transamination reactions?

Answer 8

freely reversible; direction is solely determined by concentrations of substrates and products, ie by the sign of deltaGactual

Question 9

what enzyme is used with alanine?

Answer 9

a-ketoglutarate

Question 10

what enzyme is used with glutamate?

Answer 10

oxaloacetate

Question 11

what enzyme is used with phenylalanine (histidine)?

Answer 11

transaminase

Question 12

what four amino acids cannot undergo transamination?

Answer 12

proline, hydroxyproline, lysine, threonine

Question 13

why can proline and hydroxyproline not undergo transamination

Answer 13

they are secondary amines

Question 14

why can’t lysine undergo transamination?

Answer 14

if it were to undergo transamination, its keto acid product would cyclize to form a toxic non-metabolite

Question 15

why can’t threonine undergo transamination?

Answer 15

if it were to undergo transamination, its keto acid product would dimerize into a toxic non-metabolite

Question 16

glutamate dehydrogenase

Answer 16

major route for oxidative deamination; regenerates amino group acceptor (a-ketoglutarate) and provides ammonia, either for re-utilization or disposal as urea
GDH is located within the mitochondria (important feature of urea cycle)

Question 17

glutamate dehydrogenase mechanism

Answer 17

1st half reaction oxidizes the amine to a protonated imine, with reduction (ie, hydride transfer) to form NADH
2nd half reaction hydrolyzes the imine to a keto acid

Question 18

by storing electrons, ____&______ allows cells to manage chemical energy.

Answer 18

NADH and NADPH (nature’s batteries)

Question 19

NADH oxidation yields energy needed to make 3 mol ATP from ADP & Pi through…

Answer 19

oxidative phosphorylation

Question 20

GDH uses _____ to oxidatively deaminate Glutamate, forming _______, NH4 & a-ketoglutarate

Answer 20

NAD+, NADH

Question 21

coupling of GDH and transaminases allows for…

Answer 21

oxidative degradation of other amino acids

Question 22

when operating in the opposite direction, GDH uses _____ to make glutamate by reductive amination

Answer 22

NADPH

Question 23

GDH uses …

Answer 23

NAD+ or NADPH

Question 24

the direction of the GDH reaction is determined strictly by…

Answer 24

availability of its redox coenzyme

Question 25

________ rapidly re-oxidize ______ to ______.

Answer 25

mitochondria, NADH, NAD+; NADH oxidation makes ATP in mitochondria

Question 26

NADPH is used to make…

Answer 26

fatty acids, sterols, etc

Question 27

high concentrations of ___,____,&_____ inhibit GDH

Answer 27

ATP,GTP, & NADH; reduces AA degradation & favors protein synthesis

Question 28

high concentrations of _____,____&_____ activate GDH

Answer 28

ADP,GDP,& AAs; a-KG stimulates citric acid cycle, fueling ATP synthesis
formation of a-KG tends to increase concentration of OAA, which acts like a co-catalyst, meaning it is reformed by the time the metabolic cycle ends; more OAA means cells can make more citrate, and increased TCA cycle activity means more ATP will be made within mitochondria

Question 29

_________ by GDH is part of main system for removing ammonia from amino acids/

Answer 29

oxidative deamination

Question 30

_________________ can deaminate a few amino acids by hydrolysis and elimination reactions

Answer 30

mammalian

Question 31

what catalyzes the hydrolysis of glutamine?

Answer 31

glutaminase

Question 32

what catalyzes the hydrolysis of asparagine?

Answer 32

asparaginase

Question 33

catalyzes deamination of Histidine

Answer 33

histidinase or histidine ammonia lyase