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Sintesis Asam Lemak

Sintesis Asam LemakOleh kelompok 4Mochammad Febry PratamaNinda Ramadani Herli NSifa Fauziah Dwidaraterjadi di sitoplasma khususnya pada bagian hepar dan kelenjar adiposaSintesis asam lemak terjadi apabila kelebihan Asetil-KoA.Reaksi dimulai dgn membawa asetil KoA keluar dari mitokondria ke sitoplasma melalui torak sitrat (citrate shuttle).

torak sitrat (citrate shuttle).

Source:http://themedicalbiochemistrypage.org/lipid-synthesis.php3

Citrate Shuttle (regeneration of pyruvate)

Oxaloacetate is converted back to pyruvate for re-entry into mitochondriaStep 1. Oxaloacetate + NADH + H+ malate + NAD+. Reverse of the TA cycle reaction. Catalyzed by cytosolic malate dehydrogenase.Step 2. Malate + NADP+ pyruvate + CO2 + NADPH. Catalyzed by malic enzymePyruvate translocase transports pyruvate into mitochondria.Pyruvate is converted to oxaloacetate by pyruvate carboxylase with coupled hydrolysis of one ATP. Pyruvate + ATP + CO2 + H2Ooxaloacetate + ADP + Pi (reaction of gluconeogenesis)Net Reaction: NADP+ + NADH + H+ + ATP + H2O NADPH + NAD+ + ADP + PiThus, transport of acetylCoA to cytosol requires expense of one ATP and conversion of one NADH to NADPH.Reaksi ini terjadi dalam 4 tahap dengan pemanjangan 2 atom karbon, yaitu: Condensation Reduction Dehydration reduction

Reaksi ini membutuhkan:NADPH (Reaksi Enzim Malat; HMP Shunt;Reaksi TCA) digunakan untuk sintesis sebagai reduktorATP untuk membentuk ikatan tioester pada asetil KoA dan menggabungkan CO2 pada asetil KoA menjadi malonil KoACO2

Pembentukan Malonyl-CoAReaksi ini katalisis oleh enzim Acetyl CoA Carboxylase (mengandung gugus prostetik biotin)yang diaktifkan oleh sitrat dan Insulin

Pemanjangan rantai

Sumber:harper10

Source:http://www.csun.edu/~jm77307/Fatty%20Acid%20Biosynthesis.pdf

11

Elongation of Palmitate to Stearoyl

Sintesis asam lemak tak jenuhThe double bonds of palmitoleate and oleate are introduced in vertebrates by fatty acyl-CoA desaturase, together with cytochrome b5 and cytochrome b5 reductase;

Two substrates, fatty acyl-CoA and NADPH, are oxidized simultaneously by O2 . The desaturase is thus a mixed-function oxidase.Desaturation of fatty acids:

Fatty acyl-CoA is desaturated (oxidized) using O2 and NADPH(in smooth ER)ER membrane

DIAGRAM OF SYNTHESIS

Asam lemak essensialAsam Lemak essensialAsam lemak essensial tidak dapat dihasilkan sendiri oleh tubuh karena tidak mempunyai enzim yang dapat menyisipkan ikatan ganda diluar posisi 9 di asam lemak jenuh.

Asam lemak yang essensial bagi mamalia adalah asam lemak linoleat dan -linolenat.

Sintesis asam lemak esensial22

Sintesis omega 3Fatty acid elongation and desaturase(s) systems act jointly in generation of long- and very-long-chain unsaturared fatty acids. Starting from C16 and C18, elongation specific desaturases. generate cis-monounsaturated palmitoleic acid (9,C16:1) and oleic acid (9,C18:1; Fig.1). Both palmitoleic and oleic acid are then used for the synthesis of avariety of other long-chain unsaturated fatty acidsAnimasihttp://www.wiley.com/college/fob/quiz/quiz19/19-22.htmlhttp://www.wiley.com/college/pratt/0471393878/student/animations/fatty_acid/index.htmlhttp://bio-animations.blogspot.com/2008/04/biochemistry-fatty-acid-metabolism.html