SYLLABUS 22: Amino Acids as Precursors to Molecules (other than ntds and catecholamines) Flashcards Preview

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Flashcards in SYLLABUS 22: Amino Acids as Precursors to Molecules (other than ntds and catecholamines) Deck (44):

functions of aa?

1. protein synthesis

2. energy production 

3. synthesis of biochemicals 

4. synthesis of purines, pyrimidines 

5. synthesis of other compounds 


what is glutathione? what is its structure?

the most abundant biochemical in most cells 

most important cellular antioxidant, also imp in cellular redox control 

is a tripeptide 

functions in DNA synthesis and repair, protein synthesis, iron synthesis, prostaglandin synthesis, amino acid transport, enzyme activation 

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how is glutathione synthesized?

from glutamate, cysteine, and glycine: 

1. glutamate + cysteine make gamma-glutamyl cysteine by enzyme gamma-glutamyl cysteine synthetase 

rate limiting enzyme of the pathway 

uses ATP -> ADP + Pi 


2. glycine + ATP -> ADP + Pi via glutathione synthetase 

makes GSH, glutathione


what is unique about interactions between glutamate and GSH?

gamma carboxyl group of glutamate makes the important bond w/ gamma-glutamyl-cysteine, rather than the alpha carboxyl group, which is unique 


how does GSH function in cellular redox control?

maintains sulfhydryl-disulfide equilibrium: 


2GSH + R-S-S-R' -> GSSG + RSH + R'SH 



if GSH functions as an antioxidant, how does it change and how does it return to GSH?

GSH becomes GSSG 

it is reduced back to GSH by glutathione reductase 


is trytophan essential or nonessential aa?



what important molecules can tryptophan become?

1) niacin, which becomes NAD and NADP 

2) serotonin, crucial neurotransmitter 

3) melatonin, another important neurotransmitter


how is NAD / NADP generated?

tryptophan -> niacin -> NAD or NADP


how is serotonin made?

tryptophan undergoes 

1. tryptophan hydroxylase 

2. 5'hydroxy tryptophan decarboxylase reacitons 

uses PLP as cofactor 

releases CO2 

makes serotonin 


what is serotonin

major neurotransmitter and major vasoconstrictor

important in blood pressure regulation, mood, depression


how is melatonin made

serotonin in made from tryptophan 

serotonin is converted to melatonin in a 2 step pathway 

1. acetyl CoA acetylates serotonin 

uses THB -> DHB as cofactor 

makes n-acetyl serotonin

2. N-acetyl serotonin acted on by SAM with PLP, Vit B12 as cofactors 

makes melatonin 


what is melatonin 

brain neurotransmitter important in regulating dark/light cycling so biological clock, appetite, mood 

also an important antioxidant 



what cofactors are used in tryptophan metabolism

PLP, THB, SAM, BH4 (Vit. B12)


waht aa does milk contain a lot of? effect?


makes melatonin 

makes sleepiness


what does tryptophan deficiency in diet cause?

metabolic disease, pellagra 

associated w/ energy impairment, weakness, poor motor control, cardiovascular and neurological problems, death 



how to treat pellagra?

give tryptophan or vitamin niacin in the diet 

thus generate the NAD and NADP for so many metabolic pathways 



what deficiency did people develop during the depression re: their diets 

pellagra b/c of tryptophan deficiency b/c ate lots of corn for protein 


how is trytophan metabolized in the brain?

by tryptophan hydroxylase, to 5-hydroxytryptophan 


Tryptophan + O2 + THB -> 5'hydroxytryptophan + H2O + DHB 


what are all the metabolic uses of THB as a cofactor?

THB: tetrahydrobiopterin (BH4) 

important reductant cofactor for many pathways 

1. phenylalanine -> tyrosine 

2. make catecholamines 

3. make serotonin, melatonin 

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what is creatine

an important cofactor 

made of glycine, amidino group of arginine, and methyl group from arginine via SAM

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describe creatine metabolism mechanism 

1. glycine in the kidney + SAM + part of arginine form creatine in the liver 

2. creatine undergoes creative phospho kinase, CPK, reaction, ATP->ADP. this is reversible! 

produces creatine phosphate, a high energy compound 

3. creatine pohsphate is stored in muscle, heart, and brain 

4. creatine phosphate can break down to creatinine 

creatinine is secreted in the urine, is indicative of kidney function, urine flow 


what does CPK reaction produce



where is creatine P stored

muscle, heart, brain 


how does creatine impact blood flow

when blood flow's impeded, so clots or stroke occurs, creatine P provides some ATP for energy if oxidative phosphorylation is impeded


what is creatinine

breakdown product of creatine P 

secreted in the urine and its level in the urine is indicative of kidney function, urinary flow 


how can CPK be used in diagnosis?

different isoforms of CPK exist in different tissue, so heart vs. muscle - if see elevation of heart CPK indicates heart attack, if see elevation of brain CPK indicates stroke



why is creatine phosphate important

it's a storage form of ATP 

very important in energetics - when have heart attack or stroke, and tissue is deprived of ATP for any period of time >1 minute, damage occurs 


describe glutamate decarboxylase reaction 

glutamate can be decarboxylated by glutamate decarboxylase to form GABA, gamma-amino butyric acid, a major inhibitory neurotransmitter 


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action of histadine DC?

Histidine -> Histamine, a vasodilator


functions of histamine


present in individuals w/ inflammation and allergic attacks 

also promotes secretion of pepsin and HCl 

is important in protien digestion in the stomach



function of antihistamines

prevent the vasodilatory effects of too much histamine 



what might an anti-ulcer drug target

histamine in the stomach 

b/c histamine is important in digestion 

anti-ulcer drugs are used to inhibit aciton of histamine in stomach, inhibit proteases 


function of serine DC?

Serine -> EThanolamine 

this is a major base in phospholipid phosphatidyl ethanolamine membrane structure 


function of ornithine decarboxylase?

function of products? 

Ornithine -> putrescine -> polyamines spermine and spermidine

these are nitrogenous bases that help to stabilize and bind to DNA, esp during DNA replication 


what do decarboxylases use as their cofactor?

PLP, which is from B6


how is nitric oxide made

1 step from enzyme NO synthase: 

arginine + NADPH + H+ -> citrulline + nitric oxide 

citrulline enters urea cycle, goes back to arginine 

THB is the reductant for the reaction and then NADPH 


function of NO?


regulator of blood pressure and blood flow 

prevents platelet aggregation 


what is nitroglycerin

pill that releases nitric oxide when placed under the tongue

to reduce the pain and discomfort from heart attacks and poor blood flow


what function does NO have w/ bacteria

powerful anti-bacterial agent 

reacts w/ heme-containing enzymes to block oxygen activate, eg cytochrome oxidase or cytochrome P450 

however this also impacts mammalian enzymes


nitroc oxide function in brain 



how does viagra work

contains nitric oxide 

vasodilator and blood pressure increases 

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