Cysteine: mis thiab piav qhia ntawm cov khoom

2024 Tus sau: Angel Austin | [email protected]. Kawg hloov kho: 2024-01-18 04:11

Txhua cov proteins hauv peb lub cev yog tsim los ntawm cov amino acids. Muaj ntau cov proteins hauv lub cev, thiab tsuas muaj 20 lub tsev thaiv - cov amino acids uas lawv tau tsim. Yog li, cov proteins sib txawv ntawm ib qho ntawm cov amino acids thiab lawv cov kab ke. Cysteine yog ib qho ntawm 20 amino acids.

YCysteine - yog dab tsi?

Cysteine yog ib qho aliphatic sulfur-muaj amino acid. Aliphatic - tsuas muaj saturated bonds. Zoo li txhua cov amino acid, cov mis ntawm cysteine xws li carboxyl (-COOH) thiab amino pawg (-NH _{2), nrog rau ib qho tshwj xeeb thiol (-SH). Cov thiol (lwm lub npe yog sulfhydryl) pawg suav nrog sulfur atom thiab hydrogen atom.}

Cov tshuaj molecular ntawm cysteine yog C₃H₇NO_{2S. Molecular hnyav - 121.}

Formula ntawm cov amino acid cysteine

Kev piav qhia cov qauv ntawm cov amino acids, cov qauv sib txawv yog siv. Hauv qab no yog ob peb txoj hauv kev los sau cov qauv qauv ntawm cysteine.

Txhua cov amino acids muaj cov amino thiab carboxyl pawg txuas nrog α-carbon atom, thiab sib txawv tsuas yog nyob rau hauv cov qauv ntawm radical txuas rau tib cov pa roj carbon atom. Piv txwv li, hauv qab no yog cov qauv qauv ntawm alanine, cysteine thiab glycine, serine thiab cystine.

Txhua cov amino acids muaj tib lub pob txha thiab cov radicals sib txawv. Nws yog cov qauv ntawm cov radical uas underlies qhov tsim nyog ntawm cov amino acids thiab txiav txim siab lub zog ntawm lub molecule nws tus kheej. Hauv cysteine , cov qauv radical yog CH _{2 -SH. Qhov no radical belongs rau pawg ntawm polar, uncharged, hydrophilic radicals. Qhov no txhais tau hais tias cov seem ntawm cov protein uas muaj cysteine tuaj yeem ntxiv dej (hydrate) thiab cuam tshuam nrog lwm ntu ntawm cov protein, kuj muaj cov amino acids nrog hydrophilic pawg, siv hydrogen bonds.}

Cysteine muaj ib pawg thiol tshwj xeeb

Cysteine yog ib qho amino acid tshwj xeeb. Nws tsuas yog ib qho ntawm 20 natural amino acids uas muaj thiol (-HS) pawg. Thiol pab pawg tuaj yeem raug oxidative thiab txo cov tshuaj tiv thaiv. Thaum thiol pawg ntawm cysteine yog oxidized, cystine yog tsim - ib qho amino acid uas muaj ob cysteine residues txuas nrog ib tug disulfide daim ntawv cog lus. Cov tshuaj tiv thaiv yog thim rov qab - kev kho dua tshiab ntawm daim ntawv cog lus disulfide regenerates ob cysteine molecules. Cystine disulfide bonds yog qhov tseem ceeb rau kev txiav txim siab cov qauv ntawm ntau cov proteins.

Oxidation ntawm pawg thiol ntawm cysteine ua rau tsim cov nyiaj disulfide nrog lwm tusthiol, thaum ntxiv oxidation, sulfinic thiab sulfonic acids yog tsim.

Vim nws lub peev xwm nkag mus rau hauv cov tshuaj tiv thaiv redox, cysteine muaj cov khoom antioxidant.

Cysteine yog ib feem ntawm cov proteins

Amino acids uas tsim cov proteins hu ua proteinogenic. Raws li twb tau hais lawm, muaj 20 ntawm lawv, thiab cysteine yog ib qho ntawm lawv. Txhawm rau tsim cov qauv tseem ceeb ntawm cov protein, cov amino acids tau koom ua ke los tsim cov saw ntev. Kev sib txuas tshwm sim vim yog cov pab pawg ntawm cov pob txha ntawm cov amino acids, radicals tsis koom nrog qhov no. Kev sib txuas ntawm cov amino acids yog tsim los ntawm pawg carboxyl ntawm ib cov amino acid thiab cov amino pawg ntawm lwm cov amino acid. Ib daim ntawv cog lus tsim nyob rau hauv txoj kev no ntawm ob amino acids hu ua peptide bond.

Daim duab qhia cov mis ntawm tripeptide alanine cysteine phenylalanine thiab cov txheej txheem ntawm nws tsim.

Cov peptide tsawg tshaj plaws hauv lub cev yog glutathione, uas tsuas muaj ob lub amino acids, suav nrog cysteine. Ob lub amino acids txuas ua ke hu ua dipeptide, peb hu ua tripeptide. Nov yog lwm cov qauv ntawm tripeptide ntawm alanine, lysine thiab cysteine.

Cov tshuaj muaj los ntawm 10 mus rau 40 amino acids hu ua polypeptides. Proteins lawv tus kheej muaj ntau tshaj 40 amino acid residues. Cysteine yog ib feem ntawm ntau peptides thiab proteins, xws li insulin.

Qhov chaw ntawm cysteine

Txhua hnub ib tus neeg yuav tsum haus 4.1 mg ntawm cysteine rau 1 kg ntawm lub cev hnyav. Ntawd yog, hauv tib neeg lub cevhnyav 70 kg yuav tsum tau txais 287 mg ntawm cov amino acid ib hnub twg.

Ib feem ntawm cysteine yog tuaj yeem ua rau hauv lub cev, ib feem los ntawm cov khoom noj. Cov hauv qab no yog cov npe ntawm cov khoom noj uas muaj cov amino acid ntau tshaj plaws.

Nyob zoo ib tsoom niam txiv kwv tij neej tsa phooj ywg sawv daws.

Cysteine cov ntsiab lus hauv cov khoom
khoom	Cysteine cov ntsiab lus ib 100 g ntawm cov khoom, mg
Soy khoom	638
	460
Ntaus (sunflower, watermelon, noob hnav, flax, taub dag) thiab txiv ntoo (pistachio, ntoo thuv)	451
nqaij qaib	423
	408
Pob	388
Ntaus ntses (tuna, salmon, perch, mackerel, halibut) thiab shellfish (mussels, cws)	335
YCheese, mis nyuj thiab qe	292
	127
Cereals (buckwheat, barley, rice)	120

Tsis tas li ntawd, cysteine muaj nyob rau hauv cov kua txob liab, qej, dos, zaub nplooj tsaus - Brussels sprouts, broccoli.

Tsim cov khoom noj khoom haus, xws li L-cysteine hydrochloride, N-acetylcysteine. Qhov thib ob yog soluble ntau dua thiab yooj yim dua rau lub cev nqus.

Hauv kev lag luam, L-cysteine yog tau los ntawm hydrolysis los ntawm cov plaub hau, bristles thiab tib neeg cov plaub hau. Ib qho khoom siv kim dua L-cysteine yog tsim, haum rau Muslim thiab Jewish cov kev cai noj zaub mov (raws likev cai dab qhuas).

YCysteine synthesis hauv lub cev

Y Cysteine, nrog rau tyrosine, yog ib qho tseem ceeb ntawm cov amino acid. Qhov no txhais tau hais tias lawv tuaj yeem ua ke hauv lub cev, tab sis tsuas yog los ntawm cov amino acids tseem ceeb: cysteine los ntawm methionine, tyrosine los ntawm phenylalanine.

Rau qhov kev sib txuas ntawm cysteine, xav tau ob lub amino acids - qhov tseem ceeb methionine thiab tsis tseem ceeb serine. Methionine yog sulfur atom pub. Cysteine yog tsim los ntawm homocysteine hauv ob qhov kev cuam tshuam catalyzed los ntawm pyridoxal phosphate. Cov kab mob caj ces, nrog rau qhov tsis muaj cov vitamins B ₉ (folic acid), B ₆ thiab B _{12 lead. Txhawm rau cuam tshuam kev siv cov enzyme, homocysteine hloov tsis tau mus rau cysteine, tab sis rau homocystin. Cov tshuaj no accumulates nyob rau hauv lub cev, ua rau ib tug kab mob nrog cataracts, osteoporosis, hlwb retardation.}

Kev sib xyaw hauv lub cev tuaj yeem ua rau cov neeg laus thiab cov menyuam mos tsis txaus, cov neeg muaj qee yam kab mob metabolic, kev txom nyem los ntawm malabsorption syndrome.

YCysteine synthesis cov tshuaj tiv thaiv

Nyob rau hauv tsiaj lub cev, cysteine yog synthesized ncaj qha los ntawm serine, thiab methionine yog qhov chaw ntawm leej faj. Methionine hloov mus rau homocysteine ntawm cov intermediates S-AM thiab S-AG. S-adenosylmethionine - daim ntawv nquag ntawm methionine, yog tsim los ntawm kev sib xyaw ntawm ATP thiab methionine. Ua raws li tus neeg pub dawb ntawm pawg methyl hauv kev sib txuas ntawm ntau lub tebchaw: cysteine, adrenaline, acetylcholine, lecithin, carnitine.

Raws li qhov tshwm sim ntawm transmethylation, S-AM hloov mus rau S-adenosylhomocysteine (S-AH). Thaum kawg ntawm hydrolysistsim adenosine thiab homocysteine. Homocysteine ua ke nrog serine nrog kev koom tes ntawm enzyme cystathionine-β-synthase nrog kev tsim ntawm thioether cystathionine. Cystathionine hloov mus rau cysteine thiab α-ketobutyrate los ntawm enzyme cystathionine γ-lyase.

Nyob hauv cov nroj tsuag thiab cov kab mob, synthesis tshwm sim txawv. Ntau yam tshuaj, txawm tias hydrogen sulfide, tuaj yeem ua cov sulfur rau kev sib txuas ntawm cysteine.

Lub luag haujlwm lom neeg ntawm cysteine

Vim yog pawg thiol (-HS) nyob rau hauv cov mis ntawm cysteine, disulfide bonds yog tsim nyob rau hauv cov protein, hu ua disulfide choj. Disulfide bonds yog covalent, muaj zog. Lawv yog tsim los ntawm ob cysteine molecules hauv cov protein. Intrachain txuas hniav tuaj yeem tsim nyob rau hauv ib leeg polypeptide saw, thiab txuas txuas txuas ntawm ib tus neeg cov saw hlau. Piv txwv li, ob qho tib si ntawm cov choj siv nyob rau hauv cov qauv ntawm insulin. Cov ntawv cog lus no tuav lub tertiary thiab quaternary qauv ntawm cov protein.

Disulfide bonds muaj feem ntau cov proteins uas muaj cellular. Piv txwv li, hom kev sib txuas no yog qhov tseem ceeb hauv kev ruaj khov ntawm cov qauv ntawm insulin, immunoglobulins thiab digestive enzymes. Proteins uas muaj ntau tus choj disulfide tiv taus ntau dua rau cov cua sov denaturation, tso cai rau lawv tswj lawv cov dej num nyob rau hauv cov xwm txheej hnyav dua.

Cov yam ntxwv ntawm cov qauv cysteine muab nws nrog cov khoom antioxidant. Cysteine ua lub luag haujlwm ntawm cov tshuaj tiv thaiv antioxidant, nkag mus rau hauv oxidation-txo cov tshuaj tiv thaiv. Cov pab pawg thiol muaj kev sib raug zoo rau cov hlau hnyav, yog li ntawdcov proteins uas muaj cysteine khi hlau xws li mercury, lead thiab cadmium. Lub pK ntawm cysteine nyob rau hauv cov protein yog xws li tias nws ua kom cov amino acid nyob rau hauv daim ntawv reactive thiolate, uas yog, cysteine yooj yim pub dawb rau HS anion.

Cysteine yog ib qho tseem ceeb ntawm leej faj hauv cov metabolism.

Kev ua haujlwm ntawm cysteine

Vim muaj cov pab pawg thiol uas yooj yim reacts, cysteine koom nrog ntau yam txheej txheem hauv lub cev thiab ua haujlwm ntau yam.

Muaj cov tshuaj antioxidant.
Koom nrog kev sib txuas ntawm glutathione.
Koom tes hauv kev sib txuas ntawm taurine, biotin, coenzyme A, heparin.
Koom nrog tsim cov lymphocytes.
Nws yog ib feem ntawm β-keratin, uas koom nrog tsim cov ntaub so ntswg ntawm daim tawv nqaij, plaub hau, mucous daim nyias nyias ntawm lub plab zom mov.
Txhawb nqa qhov nruab nrab ntawm qee yam tshuaj lom.