SAFEDAHO

SAFEDAHO, proteinho, moddahoi organikii kalonmolekulai tabiiero guind, ki az aminokislotaho tarkib yofta dar sokhtu faoliyati organizmho mavqei muhim dorand. Fridrikh Engels Safedahoro zaminai shakli bilogii harakati materiya donistaast. Mahz ba tufayli Safedaho dar organizm mubodilai moddaho va tabdili energiya ba vujud meoyad. Safedaho funksiyahoi muhimi fiziologiro ado mekunand. Pesh az hama Safedaho masolehi bun- yodii hujayra meboshand. Onho dar tashakkuli parda, organoid va mem- branahoi hujayra ishtirok mekunand.

Raghoi khun, pay, muy va digar juzhoi organizmhoi oli az Safedaho sokhta shudaand. Safedaho katalizatori reaksiyahoi khimiyavi dar hujayra meboshand. Vazifai muharrikii Safedaho khele muhim buda, tamomi namudhoi harakati hujayra va organizmho (kashishkhurii mushakhoi hayvonot, larzishi mijgoni soddatarinho, reaksiyai baharakatovarandai rastaniho va gayra) az Safedahoi makhsusi kashishkhuranda nobastaast. Safedaho funksiyai naqliyoti va muhofizatro niz ado mekunand. Safedai khun — gemoglobin oksigenro payvast namuda, ba tamomi bofta va uzvhoi badan mekashonad. Dar mavridi ba organizm vorid shudani modda yo hujayrahoi begona dar organizm Safedahoi makhsus — antijismho ho- sil meshavand, ki moddahoi begonaro bezarar megardonand. Safedaho manbai energiya ham meboshand. Onho dar hujayra ba aminokislotaho tajziya meshavand, ki yak qismashon baroi sintezi safeda sarf meshavand, qismi digarashon boshad purra tajziya shuda, energiyai ozod hosil mekunad. Dar vaqti tajziyai 1 gramm safeda 17,66 kJ. (4,2 kilokal) energiya judo meshavad. Khosiyati fiziki va khimiyavii Safedaho. Massai molekulai Safedaho az dahho hazor to 1 million va az on ham ziyod meshavad. Masalan, massai fermenti ribonukleaza 12700, pigmenti nafaskashii tuqumshulluk — gemosiasin 6600000 meboshad. Tarkibi aksar Safedaho 50,6—54,5% karbon, 6,5—7,3% gidrogen, 21,5—23,5% oksigen, 15—17,6% nitrogen, 0,3—2,5% sulfur dorad; dar tarkibi yak qator safedaho fosfor niz mavjud ast. Molekulai Safedaho az membranahoi nimnoqil nameguzarand; onho sust diffuziya meshavand. Halshavandagni Safedaho niz har khel ast. Bazeashon dar ob nagz hal meshavand. Baroi hal shudani bazei di- garashoi konsentrasiyai pasti namak lozim ast. Guruhi seyumi Safedaho boshand, faqat bo tasiri ishqorhoi zur hal meshavand.
Sokhti molekulai Safedaho Safedahoi organizmhoi zinda az 20 namudi aminokislotaho tarkib yoftaand. Baroi har yak safeda namudhoi muayyani aminokislotaho va tanosubi miqdorii onho khos meboshad. Dar molekulahoi Safedaho aminokislotaho bayni khud bo bandhoi peptidi (—SO—N1!–) pai ham payvast shudaand. Silsilai polipeptidie, ki aminokislotai sistin dorad, dar joi voqeshudai on bo bandi disulfidi (—8—5—) payvast shudaast. Yak safeda az safe- dai digar az rui tarkibi khud va tartibi joygirshavii aminokislota- ho dar silsilai polipeptidi komilan farq mekunad; har yak uzvi silsila yak aminokislotai muayyanu muqarrar ast. Namudhoi gunoguni Safedaho mahz az jihati sokhti avvalinashon az hamdigar farq mekunaid. Sokhti avvalini Safedahoro bo rohi ba peptidho judo kardani silsila va alohida- alohida omukhtani har yake az onon oshkor menamoyand. Dar molekulai Safedaho gayr az bandhoi peptidi va di- sulfidi boz bandhoi sershumore hastand, ki bo vujudi sust budani energiyai tasiri mutaqobilashon baroi ashkol va amaloti Safedaho ahamiyati kalon dorand. Bazan yakchand makromolekulai safeda bo ham payvast shuda, sistemai murakkabero ba vujud meorand. Masalan, gemoglobii kompleksi az chor makromolekulai hamin safeda tarkib yoftaest, ki faqat dar chunin holat oksigenro payvast karda, onro ba boftayu uzvho mekashonad. Tadqiqi sokhti molekulai Safedaho baroi minbad sintez kardani onho imkoniyat medihad. Soli 1955 sokhti mo-lekulai insulin muayyai karda shud va malum gardid, ki on az du sil- silai nisbatan kutohi polipeptidi (boqimoidai 21 va 30 aminokislota dorand) iborat ast. Badtar sokhti molekulai gemoglobin, riboiukleaza, tripsin va yak qator Safedahoi digar muayyan karda shudand. Minbad bo rohi khimiyavi peptidhoi murakkab, gormoni insulin, fermenti ribonukleaza sintez karda shudand. Alhol strukturai avvalini ziyoda az 200 safeda muayyan karda shudaast.
Tasnifi Safedaho. To hol tasnifi yagonai Safedaho mavjud nest. Hangomi tasnifi hamai Safedahoi malum tarkib, khosiyathoi fizikiyu khimiyavi va paydoishi onho, inchunin maqomi onho dar organizm ba hisob girifta meshavand. Safedaho ba du guruh taqsim meshavand. Safedahoi sodda — proteinho, ki faqat az aminokislotaho tarkib yoftaand va Safedahoi murakkab — p r o t e i d h o, ki ba tarkibashon gayr az aminokislotaho payvasthoi digar niz dokhil meshavand. Ba Safedahoi sodda albuminho, globulinho, gistonho, glutelinho, prolaminho, protaminho, proteinoidho va ba Safedahoi murakkab glikoproteidho (dar tarkibashon karbogidrat dorand), lipoproteidho (dar tarkibashon lipid dorand), nukleoproteidho (ba tarkibashon kislotahoi nukleat dokhil mesha- vand), fosfoproteidho (dar tarkibashon kislotahoi fosfat dorand) va gayra mansuband.
Biosintezi Safedaho — prosessi az aminokislotaho dar hujayrahoi organizmhoi zinda hosil shudani safedahost. Kashfi Mekhanizmi biosinteai Safedaho muvaffaqiyati kaloni ilmhoi khimiya va biologiyai solhoi 1960 asri 20 meboshad. In mekhanizm baroi hujayra va organizmhoi gunogun yak khel yo khele monand buda, dar on kislotahoi nukleat (asosan kislotai ribonukleat) ishtirok mekunand. Prosess az hisobi energiyae jarayon megirad, ki dar shakli kislotai adenoaintrifosfat (ATF) jam shudaast. Biosintezi Safedaho asosan dar ribosomaho ba amal meoyand. Sokhti avvalini silsilai polipeptidi hosilshavanda dar natijai ba ribosoma payvast shudani kislotai ribonukleati akhbor (a-kislotai ribonukleatKRN), ki on dorandai akhbor oid ba sokhti makhsusi safeda ast, ba shakl medaroyad. In akhborro a-kislotai ribonukleatKRN az kislotai dezoksiribonukleat (KDN) megirad. Aminokislotaho pesh az ba ribosoma guzashtan ba adenoaintrifosfat ATF energiya girifta faol megardand (aminokislotahoi faolgashta, omekhtai angidridi aminokislota va kislotai adenilat — aminoasiladenilat meboshand). Bad boqimondai hamin aminokislota ba kislotai ribonukleinati naqliyotii muvofiq (a-kislotai ribonukleatKRN) guzaronida meshavad. Dar in du prosess on fermente (aminoasiladonilatsintetaza yo aminoasilikislotai ribonukleat-KRN sintetaza), ki ba khudi hamoi aminokislota khos ast, ishtirok mekunad. Sipas boqimondai aminokislotas, ki bo a-kislotai ribonukleatKRN payvast shudaast, ba ribosomaho meguzarad va dar on jo silsilai polipeptidii safeda hosil meshavad. Minbad ribosomaho bo yorii a-kislotai ribonukleatKRN ba silsila payvast shuda, strukturai faoli safeda sintezkunanda — poliribosomaho yo polisomahoro hosil mekunand. Dar asosi (matrisay) kislotai dezoksiribonukleat QDN boshad a-kislotai ribonukleatKRN hosil meshavad. Mavqei har yak aminokislotai dar safedabuda ba vositai boqimondai se nuklsotid (tripletho) muayyan karda (yane ba kod darovarda) meshavad (nigared, Kodi genetiki). Dar polisomaho a-kislotai ribonukleatKRN ba kodonhoi muvofiqi a-kislotai ribonukleatKRN payvast meshavad. Barobari ba rafti silsilai nukleotid harakat’kardani (gejidani) ribosoma ba kodonhoi hamsoya molekulahoi navi a-kislotai ribonukleatKRN payvast meshavand. Dar in mavrid a-kislotai ribonukleatKRN-i avvala ozod shuda, bo nugi karboksildori khud ba aminoguruhi aminokislotai nav payvast meshavad. Hamin tavr in prosess chandin karat (to ba okhir rasidani sintez) davom karda, silsilai polipeptidi daroz shudan megirad.
Omukhtani prosesshoi biosintezi Safedaho yake az vazifahoi muhim ba shumor meravad. Vay ahamiyati ham nazariyavi va ham amali (masalan, dar tib baroi tabobati bemoriho, dar khojagii khalq baroi baland bardoshtani mahsulnokii ziroat, chorvodori va gayra) dorad.
Adabiyot: Sisakyan N. M. Gladilin K. L., Biokhimicheskie aspekti sinteza belka, dar kitobi: «Uspekhi biologicheskoy khimii», tom 7, Moskva, 1965; Shamin A. N., Razvitie khimii belka, Moskva, 1966; Vvedenie v molekulyarnuyu biologiyu (tarjumai az anglisi). Moskva. 1967. M. Samiev.