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Nitrogen Metabolism Flashcards

Nitrogen Metabolism-Amino Acids, Purines, Pyrimidines and Products Derived from Amino Acids. Pyrimidine and Purine Synthesis and Metabolism (84 cards)

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1
Q

The first committed and regulated step of purine biosynthesis

A

synthesis of phosphoribosylamine

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2
Q

Transports the bases and nucleosides to other tissue from liver

A

RBC

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3
Q

starting materials for purine breakdown

A

AMP and GMPAMP–> Adenosine –> inosine –> hypoxanthine –> xanthineAMP–> IMP–> inosine –>hypoxanthine –> xanthineGMP –> Guanosine –> Guanine –> xanthine

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4
Q

5 different precursors for purine synthesis

A

AspartateGlutamine (amide N) X2N10-Formyl-FH4 X2GlycineCo2

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5
Q

the amino group of adenine is from

A

Asp

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6
Q

dihydropyrimidine dehydrogenase

A

T+NADPH –> dihydroT + NADP

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7
Q

The two end product of the last steps of pyrimidine breakdown, Which can be used in TCA cycle

A

succinyl Co-A and Acetyl Co-AFormer from B-aminoisobutyrate and latter from B-alanine

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8
Q

The byproduct of IMP dehydrogenase

A

NADH + H+

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9
Q

the first reaction of pyrimidine breakdown starting from U

A

C —-> NH4+ + U (deamination)

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10
Q

the precursor for acetyl-coa and succinyl coa in pyrimidine breakdown

A

(U)B-alanine –>Acetyl Co-A

(T) B-aminoisobutyrate –> succinyl Co-A

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11
Q

The enzyme that catalyzes the following reaction:Adenylosuccinate –> fumarate + AMP

A

Adenylosuccinase

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12
Q

XMP

A

xanthosine monophosphate

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13
Q

adenylosuccinate synthetase catalyzes this reaction

A

Asp + IMP –> adenylosuccinate

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14
Q

Asp + IMP –> adenylosuccinate
is catalyzed by …….
Hint: the first step of AMP synthesis and requires GTP

A

adenylosuccinate synthetase

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15
Q

Most of the de novo synthesis of purine takes place in

A

liver

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16
Q

Are the sources of metabolic energy and precursors for RNA synthesis

A

ATP and GTP

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17
Q

Starting materials for pyrimidine breakdown

A

C, T

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18
Q

The products of purine breakdown

A

uric acid with low plasma solubility

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19
Q

Name all the four enzymes for the formation of AMP and GMP from IMP

A

adenylosuccinate synthetase
adenylosuccinase
IMP dehydrogenase
GMP synthase

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20
Q

The purpose and the requirements of reciprocal regulation

A

requires GTP and ATP
The purpose is to maintain balance between the synthesis of AMP and GMP:
1- AMP neg. feed back on adenylosuccinate synthetase AND
2- GMP neg. feedback on IMP dehydrogenase

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21
Q

The main source of ribose-5-phosphate

A

pentose phosphate pathway

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22
Q

The last step common for purine breakdown regardless of starting material

A

xanthine –> uric acid (Catalyzed by xanthine oxidase)

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23
Q

the first purine nucleotide

A

IMP- inosine monophosphate

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24
Q

Formation of dihydrothymine and dihydrouracil

A

rate determining steprequires NADPHEnzyme : dihydropyrimidine dehydrogenase

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25
The enzyme, reactant, products and starting reactions of purine salvage pathway
startting- Guanine / hypoxanthineGuanine + PRPP --> GMPHypoxanthine +PRPP--> IMPThe enzyme that catalyzes both reactions is HGPRT
26
an inhibitor of xanthine oxidase
allopurinol
27
Due to the high energy expense, this pathway converts free bases and nucleosides to nucleotides
Salvage pathway
28
the enzyme that catalyzes the first committed step of purine biosynthesis
GPAglutamine phosphoribosyl amidotransferase
29
HGPRT defeciency
HGPRT converts Hypoxanthine and guanine to IMP and GMP respectively.It also requires PRPP. Therefore, deficiency leads toinc uric acid as a result of dec in HGPRTand dec in PRPP and ultimately inc uric acid productionoften seen in lesch-Nyhan syndrome
30
The energy requirement for one purine synthesis
~ 6ATP
31
The first step of GMP production from IMP
E: IMP dehydrogenasehypoxanthine base is oxidized by IMPdehydrogenase to xanthine- Specifically XMP
32
Three steps for regulation of purine synthesis
1- committed step - GPA inhib by end products2- second level- PRPP synthetase (also used in salvage pathway)3- reciprocal regulation- maintains balance between the synthesis of AMP and GMP
33
donates nitrogen to XMP to form GMP
glutaminesecond step of GMP production from IMP
34
Two step production of AMPindicate the step that requires energy
1- Asp + IMP --> adenylosuccinate* It requires energy from GTP2- adenylosuccinate --> fumarate + AMP
35
Purine synthesis begins with
Attachment of amino group from Gln to ribose moiety.
36
HGPRT
hypoxanthine-guanine Phosphoribosyl transferase
37
Fumarate is released from this molecule to form AMP- Adenosine MonoPhosphate.
Adenylsuccinate
38
The amino group of guanine is from
Gln
39
The by products of Acetyl-CoA and Succinyl CoA synthesis in pyrimidine breakdown
Ammonia (used in urea cycle) and Co2
40
The enzyme that catalyzes Guanine --> Xanthine +NH4+
Guanase.GMP--> Guanosine --> guanine --> xzanthine ---> uric acid
41
phsophorylate AMP and GMP
nucleoside monophosphate kinase
42
Adenosine --?-? inosine --> hypoxanthinepurine breakdown- starting from AMP
ADAAdenosine deaminaseNH4+ forms
43
The two enzymes for the production of GMP from IMP
1- IMP dehydrogenase 2-GMP synthetase
44
The rate limiting step of pyrimidine breakdown
formation of dihydroT and dihydroU
45
pathway for uric acid conversion to urine (general-schematic)
uric acid --> blood --> sodium urate --> kidney --> urine
46
The enzyme(s) for the following reactions: hypoxanthine ---> xanthine ---> uric acid (Both release H2O2)
Xanthine oxidase
47
the step of GMP production that requires energy and the associated enxyme
GMP synthaseRequires energy from ATP
48
phosphorylates and forms ATP and GTP
nucleoside diphosphate kinase
49
The base of the first purine nucleotide
the base of IMP is hypoxanthine
50
the result of allopurinol
allopurinol is xanthine oxidase inhibitor.Xanthine oxidase catalyzes the following reactions:hypoxanthine --> xanthine --> uric acid(a series of oxidation reaction and H2O2 formation)Thus allopurinol decreases the uric acid level
51
Synthesis of inosine monophosphate
Requires 10 steps4 enzymes use ATPTwo N10-formyl-FH4 are used to donate carbons.Requires adequate dietary folate.
52
AMP--?-> IMP
AMP deaminaseNH4+ forms
53
Converts ribose-5-phosphate to PRPP
PRPP synthetase
54
megaloblastic anemia
cell division impaired due to inadequate folate
55
The product of adenine degradation
hypoxanthine
56
IMP
inosine monophosphate
57
its synthesis is catalyzed by GPA
5-phosphoribosylamine
58
the precursor for both AMP and GMP
IMP
59
#NAME?
Vitamine B12 or cobalamin
60
If intracellular [PRPP] and [Gln] are usually below GPA's Km, then an increase in their concentration leads to ...
an increase in de novo purine synthesis
61
Source of carbon for purine synthesis
two N10-formyl-FH4's
62
The product of guanine degradation
xanthine
63
GPA
glutamine phosphoribosyl amidotransferase
64
Impaired cell division as a result of inadequate folate
megaloblastic anemia
65
PRPP reaction with glutamine to form
phosphoribosylamine
66
ribose moiety
purine base is synthesized on it
67
C8 and C2 are added by ------ to the growing purine precursor.
Formyl-FH4
68
committed step in purine synthesis
PRPP + Gln ---> 5-phospshoribosylaminecatalyzed by GPA-glutamine phosphoribosyl amidotransferase
69
xanthine oxidase requires ----- to oxidize hypoxanthine.
molybdenum
70
The base of the first purine nucleotide
Hypoxanthine
71
PRPP synthetase
converts ribose-5-phosphate to PRPP, a ribose moiety on which purine is synthesized
72
The degradation of adenine produces hypoxanthine, which is oxidized to xanthine by ---------.
xanthine oxidase
73
The reason that the first step of purine synthesis is regulated on the level of substrate
bc intracellular [PRPP] and [Gln] are usually below GPA's Km.
74
It can result in high turnover tissues damage, producing megaloblastic anemia, diarrhea and glossitis.
Vit. B12 deficiency in which folate gets sequestered as 5-methyltetrahydrofolate and can't be used in purine synthesis.
75
PRPP
5'-phosphoribosyl 1'-pyrophosphate
76
AMP
Adenosine monophosphate
77
Synthesis of phosphoribosylamine is catalyzed by
GPA- glutamine phosphoribosyl amidotransferase
78
The condition in which folate gets sequestered as 5-methyltetrahydrofolate and cannot be used in purine synthesis.
B12 deficiency
79
the reduction of the ribose moiety to deoxyribose occurs at --------- level, and is catalyzed by -------- which requires thioredoxin.
at diphosphate level and catalyzed by ribonucleotide reductase (RR)
80
the base of inosine monophosphate (IMP)
hypoxanthine
81
B12 deficiency and its impact on tetrahydrofolate
tetrahydrofolate can not be generated from 5- methyltetrahydrofolate
82
the sequence of degradation of purine nucleotides
phosphate and ribose are removed first, then the nitrogenous base is oxidized.
83
The first step in purine biosynthesis produces N9 of the purine ring and is inhibited by ------- and -------.
AMP and GMP
84
The first purine nucleotide
inosine monophosphate

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