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Cisteina (prescurtat CyS sau C) este un -aminoacid neesen ial. Cisteina este implicat n

protec ia organismului, activnd globulele albe i n vindecarea rnilor. [! "ste #olosit i ca

aditiv alimentar, avnd numrul "$%&.

'ormul C*+%S

unct de topire %/& 0C

1as molar %,2 g3mol

umr 456C Cysteine

Solubil n 6p

Sources[edit!

7ietary sources[edit!

6lt8oug8 classi#ied as a non-essential amino acid, in rare cases, cysteine may be essential #or

in#ants, t8e elderly, and individuals 9it8 certain metabolic disease or 98o su##er #rom

malabsorption syndromes. Cysteine can usually be synt8esi:ed by t8e 8uman body under normal

p8ysiological conditions i# a su##icient ;uantity o# met8ionine is available. Cysteine iscataboli:ed in t8e gastrointestinal tract and blood plasma[citation needed!. 4n contrast, cystine

travels sa#ely t8roug8 t8e [?!

lant sources red peppers, garlic, onions, broccoli, brussels sprout, oats, granola, 98eat germ,

sprouted lentils.[2![unreliable source@!

Ai=e ot8er amino acids, cysteine 8as an amp8oteric c8aracter.

4ndustrial sources[edit!

B8e maority o# A-cysteine is obtained industrially by 8ydrolysis o# animal materials, suc8 as

poultry #eat8ers or 8og 8air. 7espite 9idespread belie# ot8er9ise, t8ere is little evidence t8at

8uman 8air is used as a source material and its use is eDplicitly banned in t8e "uropean 5nion.[+!

Synt8etically produced A-cysteine, compliant 9it8 Ee9is8 =os8er and 1uslim 8alal la9s, is also

available, albeit at a 8ig8er price.[F! B8e synt8etic route involves #ermentation using a mutant o#

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". coli. 7egussa introduced a route #rom substituted t8ia:olines.[$! 'ollo9ing t8is tec8nology, A-

cysteine is produced by t8e 8ydrolysis o# racemic %-amino-G%-t8ia:oline-/-carboDylic acid using

seudomonas t8ia:olinop8ilum.[&!

Hiosynt8esis[edit!

Cysteine synt8esis. Cystat8ionine beta synt8ase cataly:es t8e upper reaction and cystat8ionine

gamma-lyase cataly:es t8e lo9er reaction.

4n animals, biosynt8esis begins 9it8 t8e amino acid serine. B8e sul#ur is derived #rom

met8ionine, 98ic8 is converted to 8omocysteine t8roug8 t8e intermediate S-adenosylmet8ionine.

Cystat8ionine beta-synt8ase t8en combines 8omocysteine and serine to #orm t8e asymmetrical

t8ioet8er cystat8ionine. B8e en:yme cystat8ionine gamma-lyase converts t8e cystat8ionine into

cysteine and alp8a-=etobutyrate. 4n plants and bacteria, cysteine biosynt8esis also starts #rom

serine, 98ic8 is converted to -acetylserine by t8e en:yme serine transacetylase. B8e en:yme -

acetylserine (t8iol)-lyase, using sul#ide sources, converts t8is ester into cysteine, releasingacetate.

Hiological #unctions

B8e cysteine t8iol group is nucleop8ilic and easily oDidi:ed. B8e reactivity is en8anced 98en t8e

t8iol is ioni:ed, and cysteine residues in proteins 8ave pIa values close to neutrality, so are o#ten

in t8eir reactive t8iolate #orm in t8e cell.Hecause o# its 8ig8 reactivity, t8e t8iol group o# cysteine

8as numerous biological #unctions.

recursor to t8e antioDidant glutat8ione

7ue to t8e ability o# t8iols to undergo redoD reactions, cysteine 8as antioDidant properties.CysteineJs antioDidant properties are typically eDpressed in t8e tripeptide glutat8ione, 98ic8

occurs in 8umans as 9ell as ot8er organisms. B8e systemic availability o# oral glutat8ione ( so it must be biosynt8esi:ed #rom its constituent amino acids, cysteine, glycine, and

glutamic acid.

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proteins containing cysteine, suc8 as metallot8ionein, 9ill bind metals suc8 as mercury, lead, and

cadmium tig8tly.[?!

Loles in protein structure[edit!

4n t8e translation o# messenger L6 molecules to produce polypeptides, cysteine is coded #or by

t8e 5

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rotein disul#ide isomerases cataly:e t8e proper #ormation o# disul#ide bonds> t8e cell trans#ers

de8ydroascorbic acid to t8e endoplasmic reticulum, 98ic8 oDidises t8e environment. 4n t8is

environment, cysteines are, in general, oDidi:ed to cystine and are no longer #unctional as a

nucleop8iles.

6side #rom its oDidation to cystine, cysteine participates in numerous posttranslational

modi#ications. B8e nucleop8ilic t8iol group allo9s cysteine to conugate to ot8er groups, e.g., in

prenylation. 5bi;uitin ligases trans#er ubi;uitin to its pendant, proteins, and caspases, 98ic8

engage in proteolysis in t8e apoptotic cycle. 4nteins o#ten #unction 9it8 t8e 8elp o# a catalytic

cysteine. B8ese roles are typically limited to t8e intracellular milieu, 98ere t8e environment is

reducing, and cysteine is not oDidi:ed to cystine.

6pplications[edit!

Cysteine, mainly t8e A-enantiomer, is a precursor in t8e #ood, p8armaceutical, and personal-care

industries. ne o# t8e largest applications is t8e production o# #lavors. 'or eDample, t8e reactiono# cysteine 9it8 sugars in a 1aillard reaction yields meat #lavors.[%! A-Cysteine is also used as

a processing aid #or ba=ing.[%/!

4n t8e #ield o# personal care, cysteine is used #or permanent 9ave applications, predominantly in

6sia. 6gain, t8e cysteine is used #or brea=ing up t8e disul#ide bonds in t8e 8airJs =eratin.

Cysteine is a very popular target #or site-directed labeling eDperiments to investigate

biomolecular structure and dynamics. 1aleimides 9ill selectively attac8 to cysteine using a

covalent 1ic8ael addition. Site-directed spin labeling #or "L or paramagnetic relaDation

en8anced 1L also uses cysteine eDtensively.

4n a $$/ report released by #ive top cigarette companies, cysteine is one o# t8e ?$$ additives to

cigarettes. Ai=e most cigarette additives, 8o9ever, its use or purpose is un=no9n.[%?! 4ts

inclusion in cigarettes could o##er t9o bene#its acting as an eDpectorant, since smo=ing increases

mucus production in t8e lungs> or increasing t8e bene#icial antioDidant glutat8ione (98ic8 is

diminis8ed in smo=ers).

Leducing toDic e##ects o# alco8ol[edit!

Cysteine 8as been proposed as a preventative or antidote #or some o# t8e negative e##ects o#

alco8ol, including liver damage and 8angover. 4t counteracts t8e poisonous e##ects o#

acetalde8yde. Cysteine supports t8e neDt step in metabolism, 98ic8 turns acetalde8yde into t8e

relatively 8armless acetic acid. 4n a rat study, test animals received an A7?& dose o#

acetalde8yde. B8ose t8at received cysteine 8ad an F&M survival rate> 98en bot8 cysteine and

t8iamine 9ere administered, all animals survived.[%2! o direct evidence indicates its

e##ectiveness in 8umans 98o consume alco8ol at lo9 levels.

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-6cetylcysteine[edit!

-6cetyl-A-cysteine is a derivative o# cysteine 98erein an acetyl group is attac8ed to t8e

nitrogen atom. B8is compound is sold as a dietary supplement, and used as an antidote in cases

o# acetaminop8en overdose,[%+! and obsessive compulsive disorders suc8 as tric8otillomania.

S8eep[edit!

Cysteine is re;uired by s8eep to produce 9ool 4t is an essential amino acid t8at must be ta=en in

#rom t8eir #eed. 6s a conse;uence, during droug8t conditions, s8eep produce less 9ool> 8o9ever,

transgenic s8eep t8at can ma=e t8eir o9n cysteine 8ave been developed.[%F!

7ietary Lestrictions[edit!

B8e presence o# A-Cysteine is o#ten a point o# contention #or people #ollo9ing dietary

restrictions suc8 as Ios8er, *alal, Negan or Negetarian as it may be sourced #rom various 8uman

or animal sources.[%$! 6s a result an increasing amount o# A-Cysteine is produced via a

microbial or ot8er synt8etic processes.( 8ttps33en.9i=ipedia.org39i=i3Cysteine)

roprietatile de ba:a ale cisteinei

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Cisteina coordonea:a multe #unctii #i:iologice, #iindca se regaseste in toate tesuturile

organismului. Specialistii au constatat ca cisteina transporta nutrienti spre lim#ocite si #agocite,

care sunt celule importante ale sistemului imunitar. 7e#icienta de cisteina in organism nu este des

intalnita, vegetarienii #iind categoria cea mai eDpusa la acest risc, unul minor insa. 4n acest ca:,

e#ectul va #i slabirea sistemului imunitar. Bot in aceasta categorie, putem vorbi despre #aptul ca o

dieta saraca in vitamina H (2 si %) si in acid #olic poate duce la o absorbtie #oarte sca:uta a

cisteinei.

Cisteina mai este utila si pentru protearea ung8iilor, a parului si a pielii, #iindca sta la ba:a

#ormarii proteinei beta-=eratin.

4ata care sunt si a#ectiunile si bolile care indica #aptul ca organismul are nevoie de mai multa

cisteina sau care sunt a#ectiunile care pot #i tratate sau tinute sub control cu un aport ridicat de

cisteina

6stm>Cancer>

Cataracta>

Caderea parului>

Holi cardiovasculare>

"Dpunere toDica la metale si minereuri>

6#ectiuni ale #icatului>

soria:is>

4n#ectiile virale>

*4N3S476>

6rtrita reumatoidala.'oarte interesant, cisteina mai este recomandata de medici persoanelor care lucrea:a constant cu

ra:e O (de eDemplu in sectiile sepciale din spitale sau in aeroporturi, etc) dar si celor din

industria nucleara.

4n ce alimente gasim cisteina@

Cele mai bogate surse de cisteina sunt carnea de pui si de curcan, iaurtul, galbenusul de ou, ardeii

grasi rosii, usturoi, ceapa, broccoli, var:a de HruDelles, ova:ul si germenii de grau. Aegat de

metodele de gatire ale alimentelor, studii amanuntite au relevat #aptul ca acestea nu a#ectea:a

cantitatea de cisteina din alimente si nici calitatea acesteia. "Dista si suplimente de cisteina,

comerciali:ate sub denumirea de A-cisteina sau A-cisteina (6C) si care constau in capsule, intr-

o do:a de una, maDimum doua capsule pe :i. "ste insa necesara recomandarea prealabila a

medicului.

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"ste eDcesul de cisteina toDic@

Consumul de alimente care contin cisteina nu este cunoscut a produce e#ecte adverse, insa la

anumiti indivi:i, cu a#ectiuni speciale ale creierului, cisteina poate produce supraeDcitarea

celulelor creierului, care nu metaboli:ea:a ast#el #oarte bine aceasta substanta.

(8ttp33999.dieteti=.ro3cisteina3/%&%.8tml)