mobilization of amino acids Flashcards

1
Q

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

A

pyruvate, oxaloacetate, a-ketoglutaratew

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the central pathways in metabolism?

A

glycolysis, gluconeogenesis, Krebs Citric Acid Cycle, Oxidative Phosporylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is essential for efficient metabolism?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what do transaminases do?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

1st half reaction of enzyme-bound reactions

A

aldimine forms
converts to ketimine
hydrolyzes to ketoacid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

2nd half reaction of enzyme-bound reactions

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

know the structures of aldimine and ketimine for what?

A

enzyme bound reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is true about all transamination reactions?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what enzyme is used with alanine?

A

a-ketoglutarate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what enzyme is used with glutamate?

A

oxaloacetate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what enzyme is used with phenylalanine (histidine)?

A

transaminase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what four amino acids cannot undergo transamination?

A

proline, hydroxyproline, lysine, threonine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why can proline and hydroxyproline not undergo transamination

A

they are secondary amines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why can’t lysine undergo transamination?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why can’t threonine undergo transamination?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

glutamate dehydrogenase

A

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)

17
Q

glutamate dehydrogenase mechanism

A

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

18
Q

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

A

NADH and NADPH (nature’s batteries)

19
Q

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

A

oxidative phosphorylation

20
Q

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

A

NAD+, NADH

21
Q

coupling of GDH and transaminases allows for…

A

oxidative degradation of other amino acids

22
Q

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

23
Q

GDH uses …

A

NAD+ or NADPH

24
Q

the direction of the GDH reaction is determined strictly by…

A

availability of its redox coenzyme

25
________ rapidly re-oxidize ______ to ______.
mitochondria, NADH, NAD+; NADH oxidation makes ATP in mitochondria
26
NADPH is used to make...
fatty acids, sterols, etc
27
high concentrations of ___,____,&_____ inhibit GDH
ATP,GTP, & NADH; reduces AA degradation & favors protein synthesis
28
high concentrations of _____,____&_____ activate GDH
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
29
_________ by GDH is part of main system for removing ammonia from amino acids/
oxidative deamination
30
_________________ can deaminate a few amino acids by hydrolysis and elimination reactions
mammalian
31
what catalyzes the hydrolysis of glutamine?
glutaminase
32
what catalyzes the hydrolysis of asparagine?
asparaginase
33
catalyzes deamination of Histidine
histidinase or histidine ammonia lyase